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February 2014 CO2 Concentrations: 398.033ppm

During February 2014, the Scripps Institution of Oceanography measured an average of 398.03 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.

This value is important because 398.03 ppm is the largest CO2 concentration value for any February in recorded history.  This year’s February value is approximately 1.23 ppm higher than February 2014′s.  Month-to-month differences typically range between 1 and 2 ppm.  This particular year-to-year jump is within that range, albeit smaller than some other recent months.  For example, February 2012’s year-over-year change was +3.37 ppm and May 2012’s change was +3.02 ppm.  Of course, the unending long-term trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

The yearly maximum monthly value normally occurs during May. 2013 was no different: the 399.89ppm mean concentration in May 2013 was the highest recorded value (neglecting proxy data).  May 2013′s record will hold until the end of this month when the annual cycle pushes a monthly value above this record.  Just like in years past however, May 2014 is likely to set another new all-time monthly record (until February or March 2015 … you get the idea.)

 photo co2_widget_brundtland_600_graph_201403_zps43e6baf6.gif

Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in February from 1959 through 2014.

How do concentration measurements change in calendar years?  Let’s take a look at two charts that set that context up for us:

 photo CO2_concentration_5y_trend_NOAA_201402_zps4a54618c.png

Figure 2 – Monthly CO2 concentration values (red) from 2010 through 2014 (NOAA). Monthly CO2 concentration values with seasonal cycle removed (black). Note the yearly minimum observation occurred five months ago (red curve) and the yearly maximum value occurred nine months ago. CO2 concentrations will increase through May 2014, as they do every year, before falling again towards this year’s minimum value.

The data in this graph doesn’t look that threatening.  What’s the big deal about CO2 concentrations rising a couple of parts per million per year anyway?  The problem is the long-term rise in those concentrations and the increased heating they impart on our climate system.  Let’s take a longer view – say 50 years:

 photo CO2_concentration_50y_trend_NOAA_201402_zps39a12c50.png

Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory (NOAA).  The red curve represents the seasonal cycle based on monthly average values.  The black curve represents the data with the seasonal cycle removed to show the long-term trend (as in Figure 2).  This graph shows the relatively recent and ongoing increase in CO2 concentrations.

The big deal is, as a greenhouse gas, CO2 increases the radiative forcing toward the Earth, which over time increases the amount of energy in our climate system as heat.  This excess and increasing heat has to go somewhere or do something within the climate system because the Earth can only emit so much long wave radiation every year.  The extra heat added to the climate system within the past 15 years has almost exclusively gone into the deep ocean.  This is the result of low-frequency climate oscillations’ recent states.  That process cannot and will not last forever.  Within the next 5-15 years, those oscillations will switch phase and the excess energy will be more apparent near the Earth’s surface.  Meanwhile, the extra oceanic heat will continue to expand the ocean’s volume, which will further increase global mean sea level.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Moreover, human technologies do not yet exist that remove CO2 from any medium (air or water).  They are not likely to exist at a large-scale for some time.  Therefore, the general CO2 concentration rise in the figures above will continue for many years, with effects lasting tens of thousands of years.

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  Doing so depends primarily on the rate at which we emit CO2 into the atmosphere and secondarily how effective CO2 removal in the future is.  We can choose 400 ppm or 450 ppm or almost any other target (realistically, 350 ppm seems out of reach within the next couple hundred years).  Our concentration target value choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap; we control that timing.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.  Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating.  But the bottom line remains: We will limit future warming and climate effects when we choose to do so.


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Future Emissions Scenario Requirements & Arctic Warming [With Update]

A recent research article didn’t generate anything terribly earth-shattering, but I wanted to write about some writing on it because it deals with a recurring theme on this blog.  For context, I’ll start with the news release and article (article subs. req’d).  In a nutshell,

Climate model projections show an Arctic-wide end-of-century temperature increase of +13∘ Celsius in late fall and +5∘ Celsius in late spring if the status quo continues and current emissions increase without a mitigation scenario. In contrast, the mean temperature projection would be +7∘ Celsius in late fall and +3∘ Celsius in late spring by the end of the century if a mitigation scenario to reduce emissions is followed, concludes the paper titled, “Future Arctic Climate Changes: Adaptation and Mitigation Timescales.”

Again, there is nothing terribly shocking there.  If we do nothing, the Arctic will likely warm a whole lot more than if we implement mitigation policies.

But that paragraph could use some additional context.  What do the greenhouse gas emissions scenarios look like to generate those varying warming projections?  To get a little technical (stay with me), the authors compared two out of four of the Intergovernmental Panel on Climate Change’s (IPCC) Representative Concentration Pathways (RCPs): RCP8.5 and RCP4.5.  These pathways represent an additional 8.5 W/m^2 and +4.5 W/m^2 radiative forcing at the year 2100 relative to pre-industrial values.

But even though I’ve taken a graduate level radiation course and I’m using these same pathways in my own research, I don’t really know what +8.5 W/m^2 radiative forcing is, and neither do most people.  It’s a number with units that is not intuitively obvious.  This is where climate scientists underperform in communicating with the public and where I come in.

So instead of losing ourselves in the technical details, how can we understand what these two pathways represent?  Qualitatively, RCP8.5 represents a scenario in which we do not enact GHG mitigation policies until after the year 2100.  Economic growth and GHG emissions continue to grow throughout the rest of this century due to 4x 2000′s global energy use.  The radiative forcing is induced by 1370 ppm CO2-eq (CO2 and other GHGs).

By comparison, RCP4.5 represents a scenario that stabilizes forcing at 4.5 W/m^2 without overshooting it and has 650 ppm CO2-eq by 2100 (583 ppm CO2; 2013 mean CO2 concentration: 397 ppm).  Global energy use is just over 2x 2000 levels.  RCP4.5 achieves relatively lower CO2 concentrations by steadily decreasing the amount of carbon per energy unit supplied from 2000 to 2050, then decreasing the carbon/energy ratio very rapidly between 2050 and 2075, then leveling off from 2075-2100.  It does this via wider renewable energy deployment, but predominantly fossil fuel use with carbon capture and sequestration deployment.

In other words, RCP4.5 chiefly relies on slower CO2 concentration growth by assuming widespread and rapid deployment of technologies that do not exist today.  This point is very important to understand.

In a write-up on this same research, Joe Romm concludes thusly (emphasis mine):

This study essentially writes off the possibility of humanity doing any better:

The RCP2.6 scenario requires a 70% reduction of emissions relative to present levels by 2050, a scenario that is highly unlikely in view of the current trajectory of emissions and the absence of progress toward mitigation measures. We refer to the RCP8.5 and RCP4.5 future scenarios as business-as-usual and mitigation.

But the fact is that RCP2.6 — which is about 421 ppm CO2 — is entirely feasible from both a technical and economic perspective. It is only the irrationality, myopia, and, it would seem, self-destructiveness of Homo sapiens that make it “highly unlikely.”

No, it’s not.  RCP2.6 makes many more assumptions about technological capabilities and deployment than does RCP4.5.  It does this more quickly than RCP4.5 by modeling declining carbon per energy unit between 2010 and 2025 (which hasn’t happened yet), then declining much more rapidly starting in 2025 (only 10 years away) until 2050, then slowing down in 2050 and again in 2075.  But here is the kicker: it assumes negative carbon per energy unit after 2075!  How does it do this?  By assuming more carbon will be removed from the atmosphere than emitted into it starting in 2075 and continuing thereafter.  Do we have carbon capture and sequestration (CCS) technologies ready for rapid global deployment?  No, there is to my knowledge only a couple of utility-scale projects currently operating and they haven’t achieved the level of capture and sequestration this pathway assumes.

In order for CCS to operate at the level RCP2.6 assumes, global investment in the technology would have to increase by many factors for years.  Is there any discussion of this occurring in any government?  Will we price carbon-based fuels without interference (i.e., an end to market manipulation by fossil fuel entities and governments)?  No and these things aren’t likely to begin any time soon.

Simply put, RCP2.6 is a fantasy scenario [see update below].  Absent global economic collapse that dwarfs the Great Depression, CO2 emissions and concentrations will continue to increase as economies continue to rely on relatively cheap dirty fossil fuels with manipulated prices.  At this point, I think RCP4.5 is to a lesser extent another fantasy scenario.  That’s neither irrational nor myopic, but realistic based on historical climate policy and my own reading of where international climate policy is likely to exist in the next 35 years.  We are currently on the RCP8.5 pathway.  Researchers use RCP4.5 because it is illustratively different from RCP8.5.  They think it is technically feasible simply because they understand the likely science ramifications of RCP8.5 and misunderstand the public’s desire for continued increasing quality of life that comes with fossil fuel use.  Case in point: researchers have shown the difference between “worst-case” and “best-case” climate scenarios for 30+ years.  Nobody enacted robust climate policy in response to these comparisons.  To continue to do so moving forward is a waste of resources.

[Update]

I wanted to share some updated data demonstrating my statement that RCP2.6 and RCP4.5 are “fantasy scenarios”.  Here are two plots I used in a related post in last 2012:

 photo CO2EmissionsScenarios-hist-and-RCP-2012-b.png

Figure 1. Historical (black dots) and projected (out to 2050 only) CO2 emissions from a Nature Climate Change article (subs. req’d).  Bold colored lines (red, yellow, gray, and blue) represent IPCC AR5 RCP-related emission scenarios.   Thick green dashed lines and thin green solid lines represent SRES emission scenarios used in IPCC AR4.  Light blue dashed lines represent IS92 scenarios.  Different generation scenarios are presented together for inter-report comparison purposes.

 photo CO2EmissionsScenarios-hist-and-RCP-2012.png

Figure 2. As in Figure 1 except projections shown to year 2100 and RCP scenarios highlighted.

Figures 1 and 2 show historical and projected annual CO2 emissions in Pg/year from 1980 until 2050 and 2100, respectively.  Historical data end in 2011 because the paper was published in 2012.  So there are two more year’s data available to us now.  How do you think global CO2 emissions changed since 2011?  Did they decrease, stay the same, or increase?

It’s more challenging than it should be to find similar graphics, but I found this update:

 photo CO2_emissions_Global_Carbon_Project_2013_zps7214b665.jpg

Figure 3. Historical (1990-2012; 2013 projection) global CO2 emissions in GtC/year (1 PgC = 1 GtC).

As Figure 3 shows, global CO2 emissions rose in 2012 compared to 2011, and emissions likely rose further in 2013 compared to 2012.  It further shows that emission rates increased only by 1.0%/year in the 1990s and accelerated to 2.7%/year in the 2000s.  While recent year-0ver-year increases aren’t at 2000 mean levels, they are at least twice that of 1990 levels.  In other words, there has been no stabilization of CO2 emissions, let alone a decrease, as RCP2.6 and RCP4.5 assume.

A fair counterpoint can be made that RCP2.6 assumes a decline starting in 2020, while RCP4.5′s decline starts in 2040.  Sure enough, Figure 1 and 2 demonstrate those assumptions.  To that, I say Figure 1 and 2 also shows RCP2.6′s maximum annual emissions peak at 2010 levels.  Emissions have already increased at 2%+/year since then historically.  For argument sake, let’s say emissions will peak in 2020.  Historical emissions will then be higher than RCP2.6 assumed, which would require even more CO2 removal to achieve <2C stabilization by 2100.  More CO2 removal means more efficient and widespread deployment than RCP2.6 already assumes, which makes it less likely to occur.

RCP4.5 assumes peak annual emissions in 2040 of approximately 11 PgC/year.  If annual growth rates continue near 2.1%, we’ll actually reach that level in 2018 – 22 years ahead of RCP4.5′s assumption.  What emissions growth rate is required to hit 11 PgC/year in 2040?  See the chart below:

 photo CO2Emissions-21and0475_growth_rates_zps20b1f74a.png

Figure 4. Historical (1959-2012) and projected (2013-2040) global annual CO2 emissions using mean 2000′s emissions growth (blue) and calculated emissions required to achieve 11 GtC/year in 2040 (red).  [Historical data: 2013 Global Carbon Project.]

Note that the RCP4.5 scenario has declining emissions growth rate between 2030 and 2040 while my computations uses constant growth rate assumption.  Still, this calculation sheds some light on required changes to achieve RCP4.5 scenario assumptions.  Figure 4 shows that if future emissions grow at constant rate of 2.1%/year (less than the mean 2000′s rate; more than the mean 1990′s rate), 2040 emissions will total >17 GtC/year (remember RCP4.5′s maximum of 11 GtC/year could be achieved as early as 2018).  To max out at 11 GtC/year, emissions would either have to grow at no more than 0.475%/year – less than half the 1990′s mean value – or grow more quickly in the near future, stabilize quickly, and decrease every year following 2030.

RCP2.6 and RCP4.5 demand that countries begin to change their entire energy production fleet from fossil fuels to renewables – either immediately (RCP2.6) or within the next 10-15 years (RCP4.5).  What costs are associated with this conversion?  How many people without energy access today are denied energy access in the future?  That is something that Romm doesn’t address in his talking point that “the fact is that RCP2.6 — which is about 421 ppm CO2 — is entirely feasible from both a technical and economic perspective.”  421 ppm CO2 means no higher concentration than what will occur by 2025.

A permanent emissions decline has obviously never happened historically.  What basis allows for the assumption that it will occur starting in 2030?  More sweeping and effective policies than have ever been implemented are required.  The point to this exercise is to demonstrate that we can play games with numbers all day, but the real world is quite different from economic and climate models as well as Excel spreadsheets.  Unless and until we see real world evidence that emissions stabilization occurs, I see little reason to discuss what RCP2.6 or RCP4.5 shows beyond what “could be” as a rhetorical exercise.


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January 2014 CO2 Concentrations: 397.80ppm

During January 2014, the Scripps Institution of Oceanography measured an average of 397.80 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.

This value is important because 397.80 ppm is the largest CO2 concentration value for any January in recorded history.  This year’s January value is approximately 2.34 ppm higher than January 2013′s.  Month-to-month differences typically range between 1 and 2 ppm.  This particular year-to-year jump is just outside of that range, but is smaller than some other recent months.  For example, February 2012’s year-over-year change was +3.37 ppm and May 2012’s change was +3.02 ppm.  Of course, the unending long-term trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

The yearly maximum monthly value normally occurs during May. 2013 was no different: the 399.89ppm mean concentration in May 2013 was the highest recorded value (neglecting proxy data).  May 2013′s record will hold until the end of this month when the annual cycle pushes a monthly value above this record.  Just like in years past however, May 2014 is likely to set another new all-time monthly record (until February 2015 … you get the idea.)

 photo co2_widget_brundtland_600_graph_201402_zpsc9382547.gif

Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in January from 1959 through 2014.

How do concentration measurements change in calendar years?  Let’s take a look at two charts that set that context up for us:

 photo CO2_concentration_5y_trend_NOAA_201401_zps160d767f.png

Figure 2 – Monthly CO2 concentration values (red) from 2010 through 2014 (NOAA). Monthly CO2 concentration values with seasonal cycle removed (black). Note the yearly minimum observation occurred four months ago (red curve) and the yearly maximum value occurred eight months ago. CO2 concentrations will increase through May 2014, as they do every year, before falling again towards this year’s minimum value.

This graph doesn’t look that threatening.  What’s the big deal about CO2 concentrations rising a couple of parts per million per year anyway?  The problem is the long-term rise in those concentrations and the increased heating they impart on our climate system.  Let’s take a longer view – say 50 years:

 photo CO2_concentration_50y_trend_NOAA_201401_zps00b30f9c.png

Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory (NOAA).  The red curve represents the seasonal cycle based on monthly average values.  The black curve represents the data with the seasonal cycle removed to show the long-term trend (as in Figure 2).  This graph shows the relatively recent and ongoing increase in CO2 concentrations.

The big deal is, as a greenhouse gas, CO2 increases the radiative forcing toward the Earth, which over time increases the amount of energy in our climate system as heat.  This excess and increasing heat has to go somewhere or do something within the climate system because the Earth can only emit so much long wave radiation every year.  The extra heat added to the climate system within the past 15 years has almost exclusively gone into the deep ocean.  This is the result of low-frequency climate oscillations’ recent states.  That process cannot and will not last forever.  Within the next 5-15 years, those oscillations will switch phase and the excess energy will be more apparent near the Earth’s surface.  Meanwhile, the extra oceanic heat will continue to expand the ocean’s volume, which will further increase global mean sea level.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Moreover, human technologies do not yet exist that remove CO2 from any medium (air or water).  They are not likely to exist at a large-scale for some time.  Therefore, the general CO2 concentration rise in the figures above will continue for many years, with effects lasting tens of thousands of years.

Instead of just the past 50 years, here is a 10,000 year view of CO2 concentrations from ice cores (blue and green curves) to compare to the recent Mauna Loa observations (red):

Photobucket

Figure 4 – Historical CO2 concentrations from ice core proxies (blue and green curves) and direct observations made at Mauna Loa, Hawai’i (red curve).

This longer time series demonstrates how the curves in Figures 1 and 2 look when viewed against 10,000 additional years’ data.  Clearly, concentrations are significantly higher today than they were for thousands of years in the past.  While never completely static, the climate system our species evolved in was relatively stable in this time period.  You can see this by the relatively small changes in concentration over many hundreds of years.  Recent concentrations are an obvious aberration to recent history.

Alternatively, we could take a really, really long view:

Photobucket

Figure 5 – Historical record of CO2 concentrations from ice core proxy data (red), 2008 observed CO2 concentration value (blue circle), and 2 potential future concentration values resulting from lower (green circle) and higher (yellow circle) emissions scenarios used in the IPCC’s AR4.

Note that this graph includes values from the past 800,000 years, 2008 observed values (12ppm less than this year’s average value will be) as well as the projected concentrations for 2100 derived from a lower emissions and higher emissions scenarios used by the 2007 IPCC Fourth Assessment report.  It is clear that our planet’s climate existed within a range of CO2 concentrations between 200 and 300 ppm over the past 800,000 years.  Indeed, you would have go back millions of years into the geologic history of the planet to find the last time CO2 concentrations were near 400 ppm.  And let me be clear, the global climate then was much different from today: the globe was much warmer, there were no polar ice caps, and ecosystems were radically different from today’s.  That’s not to say today’s climate is “better” or “worse” than a paleoclimate.  It is to say that today’s ecosystems do not exist in the climate humans are forcing on the planet.

If our current emissions rate continues unabated, it looks like a tripling of average pre-industrial (prior to 1850) concentrations will be our future reality: 278ppm * 3 = 834ppm.  This graph also clearly shows how significant projected emission pathways could be when we compare them to the past 800,000 years.  It is important to realize that we are currently on the higher emissions pathway (towards 800+ppm; yellow dot), not the lower emissions pathway.

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  Doing so depends primarily on the rate at which we emit CO2 into the atmosphere and secondarily how effective CO2 removal in the future is.  We can choose 400 ppm or 450 ppm or almost any other target (realistically, 350 ppm seems out of reach within the next couple hundred years).  Our concentration target value choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap; we control that timing.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.  Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating.  But the bottom line remains: We will limit future warming and climate effects when we choose to do so.


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December 2013 CO2 Concentrations: 396.81ppm

During December 2013, the Scripps Institution of Oceanography measured an average of 395.10 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.

This value is important because 395.10 ppm is the largest CO2 concentration value for any December in recorded history.  This year’s December value is approximately 2 ppm higher than December 2012′s.  Month-to-month differences typically range between 1 and 2 ppm.  This particular year-to-year jump is just outside of that range, but is smaller than some other recent months.  For example, February 2012’s year-over-year change was +3.37 ppm and May 2012’s change was +3.02 ppm.  Of course, the unending long-term trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

The yearly maximum monthly value normally occurs during May. 2013 was no different: the 399.89ppm mean concentration in May 2013 was the highest value reported last year (neglecting proxy data).  May 2013′s record will hold until the end of February 2014 when the annual cycle pushes a monthly value above the record.  Just like in years past however, May 2014 is likely to set another new all-time monthly record (until February 2015 … you get the idea.)

How do concentration measurements change in calendar years?  Let’s take a look at two charts that set that context up for us:

 photo CO2_concentration_5y_trend_NOAA_201312_zpse6bb2b3c.png

Figure 1 – Monthly CO2 concentration values (red) from 2009 through 2014 (NOAA). Monthly CO2 concentration values with seasonal cycle removed (black). Note the yearly minimum observation occurred three months ago (red curve) and the yearly maximum value occurred seven months ago. CO2 concentrations will increase through May 2014, as they do every year, before falling again towards this year’s minimum value.

This graph doesn’t look that threatening.  What’s the big deal about CO2 concentrations rising a couple of parts per million per year anyway?  The problem is the long-term rise in those concentrations and the increased heating they impart on our climate system.  Let’s take a longer view – say 50 years: photo CO2_concentration_50y_trend_NOAA_201312_zpscc6d916c.png

Figure 2 – 50 year time series of CO2 concentrations at Mauna Loa Observatory (NOAA).  The red curve represents the seasonal cycle based on monthly average values.  The black curve represents the data with the seasonal cycle removed to show the long-term trend (as in Figure 1).  This graph shows the relatively recent and ongoing increase in CO2 concentrations.

The big deal is, as a greenhouse gas, CO2 increases the radiative forcing toward the Earth, which over time increases the amount of energy in our climate system as heat.  This excess and increasing heat has to go somewhere or do something within the climate system because the Earth can only emit so much long wave radiation every year.  Additional figures below show where most of the heat has gone recently.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Moreover, human technologies do not yet exist that remove CO2 from any medium (air or water).  They are not likely to exist at a large-scale for some time.  Therefore, the general CO2 concentration rise in the figures above will continue for many years, with effects lasting tens of thousands of years.

This month, I will once again present some graphs that provide additional context for CO2 concentration.  Here is a 10,000 year view of CO2 concentrations from ice cores to compare to the recent Mauna Loa observations:

Photobucket

Figure 3 – Historical CO2 concentrations from ice core proxies (blue and green curves) and direct observations made at Mauna Loa, Hawai’i (red curve).

This longer time series demonstrates how the curves in Figures 1 and 2 look when viewed against 10,000 additional years’ data.  Clearly, concentrations are significantly higher today than they were for thousands of years in the past.  While never completely static, the climate system our species evolved in was relatively stable in this time period.  You can see this by the relatively small changes in concentration over many hundreds of years.  Recent concentrations are an obvious aberration to recent history.

Alternatively, we could take a really, really long view:

Photobucket

Figure 4 – Historical record of CO2 concentrations from ice core proxy data (red), 2008 observed CO2 concentration value (blue circle), and 2 potential future concentration values resulting from lower (green circle) and higher (yellow circle) emissions scenarios used in the IPCC’s AR4.

Note that this graph includes values from the past 800,000 years, 2008 observed values (10ppm less than this year’s average value will be) as well as the projected concentrations for 2100 derived from a lower emissions and higher emissions scenarios used by the 2007 IPCC Fourth Assessment report.  It is clear that our planet’s climate existed within a range of CO2 concentrations between 200 and 300 ppm over the past 800,000 years.  Indeed, you would have go back millions of years into the geologic history of the planet to find the last time CO2 concentrations were near 400 ppm.  And let me be clear, the global climate then was much different from today: the globe was much warmer, there were no polar ice caps, and ecosystems were radically different from today’s.  That’s not to say today’s climate is “better” or “worse” than a paleoclimate.  It is to say that today’s ecosystems do not exist in the climate humans are forcing on the planet.

If our current emissions rate continues unabated, it looks like a tripling of average pre-industrial (prior to 1850) concentrations will be our future reality: 278ppm * 3 = 834ppm.  This graph also clearly shows how significant projected emission pathways could be when we compare them to the past 800,000 years.  It is important to realize that we are currently on the higher emissions pathway (towards 800+ppm; yellow dot), not the lower emissions pathway.

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  Doing so depends primarily on the rate at which we emit CO2 into the atmosphere and secondarily how effective CO2 removal in the future is.  We can choose 400 ppm or 450 ppm or almost any other target (realistically, 350 ppm seems out of reach within the next couple hundred years).  Our concentration target value choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap; we control that timing.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.  Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating.  But the bottom line remains: We will limit future warming and climate effects when we choose to do so.


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Denver’s September 2013 Climate Summary

Temperature

During the month of September 2013, Denver, CO’s (link updated monthly) temperatures were 2.8°F above normal (66.4°F vs. 63.6°F).  The National Weather Service recorded the maximum temperature of 97°F on the 5th and 6th; they recorded the minimum temperature of 38°F on the 28th.  Here is the Denver temperature September 2013 time series:

 photo Denver_Temps_201309_zps687d6b03.png

Figure 1. Time series of temperature at Denver, CO during September 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

The month started off with a heat wave, as a result of an anomalous high pressure ridge over the western US.  It’s not obvious on this chart, but the week of September 8th ushered in a big change from the early month heat wave, which I discuss in the precipitation section below.

Denver’s temperature was above normal for the past five consecutive months.  May 2013 ended a short streak of four months with below normal temperatures.  Looking back a little further in time, October 2012 broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Through September, 2013, there were 57 90°F+ days in 2013, which means 2013 gained sole 4th place status of most 90°F days in one year.  Last year, the hottest summer on record for Denver, there was an astounding 73 90°F+ days!  Thankfully, this year also featured far fewer 100°F+ days than 2012: 2 instead of 13 (a record number).  After last year’s record hot summer, summer 2013 felt comparatively cool, which just goes to show how truly monumental last year’s records were.

I haven’t determined if the NWS (or anyone else) collects record high minimum temperatures (warm nighttime lows) in a handy table, chart, or time series.  Denver’s 68°F on Sep. 3rd was such a record (previously 67, set in 1947), as was Sep. 4th’s 69°F (previously 64°F, set in 1995 and previous years).  I’m curious how Denver’s nightly lows have changed in the past 100+ years.  If I find or put something together, I’ll include it in a future post.

Precipitation

Instead of amazing temperature records (although 97°F in September is very hot!), September saw precipitation records.  Total precipitation was much greater than normal during September 2013: 5.61″ precipitation fell at Denver during the month instead of the normal 0.92″!  Most of this fell at DIA on the 14th and 12th of the month (2.01″ and 1.11″).  As I wrote about after the event, Denver and other communities with similar rain totals paled in comparison to southern Aurora and Boulder, which received over 18″ of rain in one week, and more for the month!  Given that the normal annual total precipitation for these places is 15″, Denver and other places received over 1/3 of their yearly annual precipitation total in one month – a month that is normally relatively dry.

During the week of the 8th, the confluence of a slow-moving upper-level low, a surface stationary front, and tropical moisture from both the Pacific Ocean and Gulf of Mexico generated record rainfall over the northern Front Range of Colorado, including Denver.  This rainfall led to devastating flooding, from which communities are just beginning to recover.  About the only good news from this natural disaster is it busted the area’s long-term drought.

Interannual Variability

I have written literally hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


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September 2013 CO2 Concentrations: 393.31ppm

During September 2013, the Scripps Institution of Oceanography measured an average of 393.31 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.

This value is important because 393.31 ppm is the largest CO2 concentration value for any September in recorded history.  This year’s September value is 2.17 ppm higher than September 2012′s.  Month-to-month differences typically range between 1 and 2 ppm.  This particular year-to-year jump is just outside of that range.  This year-to-year change is smaller than some other months this year.  For example, February’s year-over-year change was +3.37 ppm and May’s change was +3.02 ppm.  Of course, the unending trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

The yearly maximum monthly value normally occurs during May. This year was no different: the 399.89ppm mean concentration in May 2013 was the highest value reported this year and, prior to the last six months, in recorded history (neglecting proxy data).  I expected May of this year to produce another all-time record value and it clearly did that.  May 2013′s value will hold onto first place all-time until February 2014, due to the annual CO2 oscillation that Figure 2 displays.

 photo co2_widget_brundtland_600_graph_201309_zpsa98224c9.gif

Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in September from 1958 through 2013.

CO2Now.org added the `350s` to the past few month’s graphics.  I suppose they’re meant to imply concentrations shattered 350 ppm back in the 1980s.  Interestingly, they removed the `400s` from this month’s graph.  So concentrations within 5ppm of a threshold are added to CO2now.org’s graphic.

How do concentration measurements change in calendar years?  Normally, I insert two NOAA graphs here showing 5-year and 50-year raw monthly values and monthly values with the annual trend removed.  Unfortunately, due to the government shutdown, NOAA is not updating their graphics.  As a side note, I also cannot retrieve NOAA and NASA data for my own research.

As a greenhouse gas, CO2 increases the radiative forcing of the Earth, which increases the amount of energy in our climate system as heat.  This excess and increasing heat has to go somewhere or do something within the climate system because the Earth can only emit so much long wave radiation every year.  Additional figures below show where most of the heat has gone recently.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Moreover, human technologies do not yet exist that remove CO2 from any medium (air or water).  They are not likely to exist for some time.  Therefore, the general CO2 concentration rise in Figure 1 will continue for many years, with effects lasting tens of thousands of years.

This month, I will once again present some graphs that provide additional context for CO2 concentration.  Here is a 10,000 year view of CO2 concentrations from ice cores to compare to the recent Mauna Loa observations:

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Figure 4 – Historical CO2 concentrations from ice core proxies (blue and green curves) and direct observations made at Mauna Loa, Hawai’i (red curve).

Clearly, concentrations are significantly higher today than they were for thousands of years in the past.  While never completely static, the climate system our species evolved in was relatively stable in this time period.

Alternatively, we could take a really, really long view:

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Figure 5 – Historical record of CO2 concentrations from ice core proxy data (red), 2008 observed CO2 concentration value (blue circle), and 2 potential future concentration values resulting from lower (green circle) and higher (yellow circle) emissions scenarios used in the IPCC’s AR4.

Note that this graph includes values from the past 800,000 years, 2008 observed values (10ppm less than this year’s average value will be) as well as the projected concentrations for 2100 derived from a lower emissions and higher emissions scenarios used by the 2007 IPCC Fourth Assessment report.  If our current emissions rate continues unabated, it looks like a tripling of average pre-industrial (prior to 1850) concentrations will be our future reality: 278ppm * 3 = 834ppm.  This graph also clearly demonstrates how anomalous today’s CO2 concentration values are in the context of paleoclimate.  It further shows how significant projected emission pathways could be when we compare them to the past 800,000 years.  It is important to realize that we are currently on the higher emissions pathway (towards 800+ppm; yellow dot).  The last time atmospheric CO2 concentrations were that high, the globe was much warmer, there were no polar ice caps, and ecosystems were radically different from today’s.

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  Doing so depends primarily on the rate at which we emit CO2 into the atmosphere.  We can choose 400 ppm or 450 ppm or almost any other target (realistically, 350 ppm seems out of reach within the next couple hundred years).  Our concentration target value choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap; we control that timing.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.  Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating.  But the bottom line remains: We will limit future warming and climate effects when we choose to do so.


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NASA & NOAA: August 2013 4th Warmest Globally On Record

According to data released by NASA and NOAA this month, August was the 4th warmest August globally on record.  Here are the data for NASA’s analysis; here are NOAA data and report.  The two agencies have different analysis techniques, which in this case resulted in different temperature anomaly values but the same overall rankings within their respective data sets.  The analyses result in different rankings in most months.  The two techniques do provide a check on one another and confidence for us that their results are robust.  At the beginning, I will remind readers that the month-to-month and year-to-year values and rankings matter less than the long-term climatic warming.  Monthly and yearly conditions changes primarily by the weather, which is not climate.

The details:

August’s global average temperature was 0.62°C (1.12°F) above normal (1951-1980), according to NASA, as the following graphic shows.  The past three months have a +0.58°C temperature anomaly.  And the latest 12-month period (Aug 2012 – Jul 2013) had a +0.59°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The 2010-2012 downturn was largely due to the latest La Niña event (see below for more) that ended early last summer.  Since then, ENSO conditions returned to a neutral state (neither La Niña nor El Niño).  Therefore, as previous anomalously cool months fall off the back of the running mean, and barring another La Niña, the 12-month temperature trace should track upward again throughout 2013.

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Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through August 2013 from NASA.

According to NOAA, April’s global average temperatures were 0.62°C (1.12°F) above the 20th century average of 15.6°C (60.1°F).  NOAA’s global temperature anomaly map for August (duplicated below) shows where conditions were warmer and cooler than average during the month.

 photo NOAA-Temp_Analysis_201308_zpsf2f24a41.gif

Figure 2. Global temperature anomaly map for August 2013 from NOAA.

The two different analyses’ importance is also shown by the preceding two figures.  Despite differences in specific global temperature anomalies, both analyses picked up on the same temperature patterns and their relative strength.

 photo NinoSSTAnom20130924_zps74ba969c.gif

Figure 3. Time series of weekly SST data from NCEP (NOAA).  The highest interest region for El Niño/La Niña is NINO 3.4 (2nd time series from top).

The last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012.  Since then, tropical Pacific sea-surface temperatures peaked at +0.8 (y-axis) in September 2012.  You can see the effect on global temperatures that the last La Niña had via this NASA time series.  Both the sea surface temperature and land surface temperature time series decreased from 2010 (when the globe reached record warmth) to 2012.  Recent ENSO events occurred at the same time that the Interdecadal Pacific Oscillation entered its most recent negative phase.  This phase acts like a La Niña, but its influence is smaller than La Niña.  So natural, low-frequency climate oscillations affect the globe’s temperatures.  Underlying these oscillations is the background warming caused by humans, which we detect by looking at long-term anomalies.  Despite these recent cooling influences, temperatures were still top-10 warmest for a calendar year (2012) and during individual months, including August 2013.

Skeptics have pointed out that warming has “stopped” or “slowed considerably” in recent years, which they hope will introduce confusion to the public on this topic.  What is likely going on is quite different: since an energy imbalance exists (less energy is leaving the Earth than the Earth is receiving; this is due to atmospheric greenhouse gases) and the surface temperature rise has seemingly stalled, the excess energy is going somewhere.  The heat has to be going somewhere – energy doesn’t just disappear.  That somewhere is likely the oceans, and specifically the deep ocean (see figure below).  Before we all cheer about this (since few people want surface temperatures to continue to rise quickly), consider the implications.  If you add heat to a material, it expands.  The ocean is no different; sea-levels are rising in part because of heat added to it in the past.  The heat that has entered in recent years won’t manifest as sea-level rise for some time, but it will happen.  Moreover, when the heated ocean comes back up to the surface, that heat will then be released to the atmosphere, which will raise surface temperatures as well as introduce additional water vapor due to the warmer atmosphere.  Thus, the immediate warming rate might have slowed down, but we have locked in future warming (higher future warming rate).

 photo Ocean_heat_content_balmaseda_et_al_zps23184297.jpg

Figure 4. New research that shows anomalous ocean heat energy locations since the late 1950s.  The purple lines in the graph show how the heat content of the whole ocean has changed over the past five decades. The blue lines represent only the top 700 m and the grey lines are just the top 300 m.  Source: Balmaseda et al., (2013)

Paying for recovery from seemingly localized severe weather and climate events is and always will be more expensive than paying to increase resilience from those events.  As drought continues to impact the US, as Arctic ice continues its long-term melt, as storms come ashore and impacts communities that are not prepared for today’s high-risk events (due mostly to poor zoning and destruction of natural protections), economic costs will accumulate in this and in future decades.  It is up to us how many costs we subject ourselves to.  As President Obama begins his second term with climate change “a priority”, he tosses aside the most effective tool available and most recommended by economists: a carbon tax.  Every other policy tool will be less effective than a Pigouvian tax at minimizing the actions that cause future economic harm.  It is up to the citizens of this country, and others, to take the lead on this topic.  We have to demand common sense actions that will actually make a difference.

But be forewarned: even if we take action today, we will still see more warmest-ever La Niña years, more warmest-ever El Niño years, more drought, higher sea levels, increased ocean acidification, more plant stress, and more ecosystem stress.  The biggest difference between efforts in the 1980s and 1990s to scrub sulfur and CFC emissions and future efforts to reduce CO2 emissions is this: the first two yielded an almost immediate result.  It will take decades to centuries before CO2 emission reductions produce tangible results humans can see.  That is part of what makes climate change such a wicked problem.


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August 2013 CO2 Concentrations: 395.15 ppm

During August 2013, the Scripps Institution of Oceanography measured an average of 395.15 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.

This value is important because 395.15 ppm is the largest CO2 concentration value for any August in recorded history.  This year’s July value is 2.74 ppm higher than August 2012′s!  Month-to-month differences typically range between 1 and 2 ppm.  This particular year-to-year jump is clearly well outside of that range.  This change is in line with other months this year: February’s year-over-year change was +3.37 ppm and May’s change was +3.02 ppm.  Of course, the unending trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

The yearly maximum monthly value normally occurs during May. This year was no different: the 399.89ppm mean concentration in May 2013 was the highest value reported this year and, prior to the last six months, in recorded history (neglecting proxy data).  I expected May of this year to produce another all-time record value and it clearly did that.  May 2013′s value will hold onto first place all-time until February 2014, due to the annual CO2 oscillation that Figure 2 displays.

 photo co2_widget_brundtland_600_graph_201308_zpsf4c5a266.gif

Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in August from 1958 through 2013.

CO2Now.org added the `350s` and `400s` to the past few month’s graphics.  I suppose they’re meant to imply concentrations shattered 350 ppm back in the 1980s and are pushing up against 400 ppm now in the 2010s.  I’m not sure that they add much value to this graph, but perhaps they make an impact on most people’s perception of milestones within the trend.

How do concentration measurements change in calendar years?  The following two graphs demonstrate this.

 photo CO2_concentration_5y_trend_NOAA_201309_zps94520ee9.png

Figure 2 – Monthly CO2 concentration values (red) from 2009 through 2013 (NOAA). Monthly CO2 concentration values with seasonal cycle removed (black). Note the yearly minimum observation occurred ten months ago and the yearly maximum value occurred three months ago. CO2 concentrations will decrease through October 2013, as they do every year after May, before rebounding towards next year’s maximum value.  The red points and line demonstrate the annual CO2 oscillation that exists on top of the year-over-year increase, which the black dots and line represents.

This graph doesn’t look that threatening.  What’s the big deal about CO2 concentrations rising a couple of parts per million per year anyway?  The problem is the long-term rise in those concentrations and the increased heating they impart on our climate system.  Let’s take a longer view – say 50 years:

 photo CO2_concentration_50y_trend_NOAA_201309_zps7649367a.png

Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory (NOAA).  The red curve represents the seasonal cycle based on monthly average values.  The black curve represents the data with the seasonal cycle removed to show the long-term trend (as in Figure 2).  This graph shows the relatively recent and ongoing increase in CO2 concentrations.

As a greenhouse gas, CO2 increases the radiative forcing of the Earth, which increases the amount of energy in our climate system as heat.  This excess and increasing heat has to go somewhere or do something within the climate system because the Earth can only emit so much longwave radiation every year.  Additional figures below show where most of the heat has gone.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Human technologies do not yet exist that remove CO2 from any medium (air or water).  They are not likely to exist for some time.  Therefore, the general CO2 concentration rise in Figures 2 and 3 will continue for many years.

This month, I will once again present some graphs that provide additional context for CO2 concentration.  Here is a 10,000 year view of CO2 concentrations from ice cores to compare to the recent Mauna Loa observations:

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Figure 4 – Historical CO2 concentrations from ice core proxies (blue and green curves) and direct observations made at Mauna Loa, Hawai’i (red curve).

Clearly, concentrations are significantly higher today than they were for thousands of years in the past.  While never completely static, the climate system our species evolved in was relatively stable in this time period.

Or we could take a really, really long view:

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Figure 5 – Historical record of CO2 concentrations from ice core proxy data, 2008 observed CO2 concentration value, and 2 potential future concentration values resulting from lower and higher emissions scenarios used in the IPCC’s AR4.

Note that this graph includes values from the past 800,000 years, 2008 observed values (10ppm less than this year’s average value will be) as well as the projected concentrations for 2100 derived from a lower emissions and higher emissions scenarios used by the 2007 IPCC Fourth Assessment report.  If our current emissions rate continues unabated, it looks like a tripling of average pre-industrial (prior to 1850) concentrations will be our future reality: 278 * 3 = 834.  This graph also clearly demonstrates how anomalous today’s CO2 concentration values are in the context of paleoclimate.  It further shows how significant projected emission pathways could be when we compare them to the past 800,000 years.  It is important to realize that we are currently on the higher emissions pathway (towards 800+ppm; yellow dot).

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  It depends primarily on the rate at which we emit CO2 into the atmosphere.  We can choose 400 ppm or 450 ppm or almost any other target (realistically, 350 ppm seems out of reach within the next couple hundred years).  That choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap; we control that timing.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.  Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating.  But the bottom line remains: We will limit future warming and climate effects when we choose to do so.

I mentioned above that CO2 is a greenhouse gas.  If CO2 concentrations were very low, the average temperature of the planet would be 50°F cooler.  Ice would cover much more of the planet’s surface than it does today.  So some CO2 is a good thing.  The problem with additional CO2 in the atmosphere is that it throws off the radiative balance of the past 10,000 years.  This sets in motion a set of consequences, most of which we cannot anticipate simply because our species has never experienced them.  The excess heat absorbed by the climate system went to the most efficient heat sink on our planet, the oceans:

 photo Total-Heat-Content.gif

Figure 6 – Heat content anomaly from 1950 to 2004 from Murphy et al., 2009 (subs. req’d).

20th century global surface temperature rise measured +0.8°F.  That relatively small increase, which is already causing widespread effects today, is a result of the tiny heat content anomaly shown in red in Figure 6.  This situation continued since Murphy’s 2009 publication

 photo Ocean_heat_content_balmaseda_et_al_zps23184297.jpg

Figure 7 – Oceanic heat content by depth since 19

This figure shows where most of the excess heat went since 2000: the deep ocean (>700m depth).  The heat content change of the upper 300m increased by 5 * 10^22 Joules/year in that time (and most of that in the 2000-2003 time span) while the 300-700m layer’s heat increased by an additional 5 * 10^22 J/y and the >700m ocean’s heat increased by a further 8 * 10^22 J/y.  That’s a lot of energy.  How much energy is it?  In 2008 alone, the oceans absorbed as much energy as 6.6 trillion Americans used in the same year.  Since there is only 7 billion people on the planet, the magnitude of this energy surplus is staggering.

More to the point, deep water heat content continued to surge with time while heat content stabilized in the ocean’s top layers.   Surface temperature measurements largely reflect the top layer of the ocean.  If heat content doesn’t change with time in those layers, neither will sea surface temperatures.  The heat is instead going where we cannot easily measure it.  Does that mean “global warming has stopped” as some skeptics recently claimed?  No, it means the climate system is transferring the heat where and when it can.  If the deep ocean can more easily absorb the heat than other media, then the heat will go there.

The deep ocean will not permanently store this heat however.  The globe’s oceans turn over on long time scales.  The absorbed heat will come back to the surface where it can transfer to the atmosphere, at which point we will be able to easily detect it again.  So at some point in the future, perhaps decades or a century from now, a temperature surge could occur.  We have been afforded time that many scientists did not think we had to mitigate and adapt to the changing climate.  That time is not limitless.


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Denver’s August 2013 Climate Summary

Temperature

During the month of August 2013, Denver, CO’s (link updated monthly) temperatures were 2.1°F above normal (74.6°F vs. 72.5°F).  The National Weather Service recorded the maximum temperature of 99°F on the 20th and they recorded the minimum temperature of 52°F on the 9th.  Here is the time series of Denver temperatures in August 2013:

 photo Denver_Temps_201308_zps974cdaa4.png

Figure 1. Time series of temperature at Denver, CO during August 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

The month started off cooler than normal as this year’s very active monsoon continued well into August 2013.  High pressure began to dominate the region again in the middle of the month.  Note the large number of days with daily mean temperatures equal to or greater than 78°F.  This was mainly due to the excessive nighttime heat (note the blue line above the climatological normal lows), but also the daily high temperatures in the mid to upper-90s.

Denver’s temperature was above normal for the past four months in a row.  May 2013 ended a short streak of four months with below normal temperatures.  October 2012 broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Through September 4th, 2013, there were 50 90°F+ days in 2013, which ties three other years (1960, 1964, 2011) for 10th most 90°F days.  As of September 5th, the NWS forecast calls for an additional four days with maximum temperatures equal to or greater than 90°F, which would push the yearly total to 54, good for a tie for sixth place.  Last year, the hottest summer on record for Denver, there was an astounding 73 90°F+ days!  Thankfully, this year also featured far fewer 100°F+ days than 2012: 2 instead of 13 (a record number).

I haven’t determined if the NWS (or anyone else) collects record high minimum temperatures (warm nighttime lows) in a handy table, chart, or time series.  Denver’s 68°F on Sep. 3rd was such a record (previously 67, set in 1947), as was Sep. 4th’s 69°F (previously 64°F, set in 1995 and previous years).  I’m curious how Denver’s nightly lows have changed in the past 100+ years.  If I find or put something together, I’ll include it in a future post..

Precipitation

Precipitation was greater than normal during August 2013: 2.78″ precipitation fell at Denver during the month instead of the normal 1.69″.  Most of this fell at DIA on the 22nd of the month (1.94″).  This wasn’t the case for every location in the Denver metro area however since precipitation is such a variable phenomenon.

Precipitation that fell during the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a mid-August 2013 post.  Almost all of Colorado continues under at least some measure of drought in early September 2013 (the exception being along the Front Range in northern Colorado, which received almost daily monsoon rainfall in August).  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however.  The good news is this area shrank in the last month or so.  Colorado still needs the jet stream to substantially shift position this fall and next spring in order to receive the amount of precipitation required to break the long-term drought.  The last NWS 3-month projection didn’t indicate that this was likely to happen.  Hopefully, for the state’s sake, I hope the NWS is wrong.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


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Denver’s July 2013 Climate Summary

Temperature

During the month of July 2013, Denver, CO’s (link updated monthly) temperatures were 0.1°F above normal (74.3°F vs. 74.2°F).  The National Weather Service recorded the maximum temperature of 100°F on the 11th and they recorded the minimum temperature of 55°F on the 2nd.  Here is the time series of Denver temperatures in July 2013:

 photo Denver_Temps_201307_zps3eecd5f9.png

Figure 1. Time series of temperature at Denver, CO during July 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

Compared to spring 2013, June and July brought less extreme weather to the Denver area.   After a very warm start to the month’s temperature due to high pressure that covered the area since mid-June, cooler temperatures were the rule for the 2nd half of the month.  This change was due to an active monsoon season.  Clouds formed nearly every day and the NWS measured rain 9 out of the last 18 days of the month – a big change from last year.

Denver’s temperature was above normal for the past three months (May- June-July).  May 2013 ended a short streak of four months with below normal temperatures.  Seven of the past twelve months were warmer than normal.  October finally broke last year’s extreme summer heat, which included the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Precipitation

Precipitation was lighter than normal during July 2013: only 1.98″ precipitation fell at Denver during the month instead of the normal 2.16″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received rainfall on days that the official Denver recording site did not, which is the usual case for convective-type precipitation.

Precipitation that fell during the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a mid-August 2013 post.  Almost all of Colorado continues under at least some measure of drought in early September 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however and the area with D4 conditions slowly expanded during the past few months.  Absent a significant shift in the upper-level jet stream’s position, the NWS expects dry conditions to persist over CO during the next one to three months, which will likely worsen drought conditions.

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