Weatherdem's Weblog

Bridging climate science, citizens, and policy


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Future Emissions Scenario Requirements Part II

Ask and ye shall receive.  I recently wrote about what future GHG emissions scenarios included in terms of emission reduction requirements.  I have maintained for some time now that most of the IPCC’s emission and concentration scenarios are essentially useless for practical planning purposes.  Sure, they’re interesting academically, but we climate scientists can’t just study something for the sake of studying it in today’s tight federal budget environment.

In that post, I showed some graphics from a 2013 Nature paper which combined historical emissions as well as projected emissions.  Due to the article’s age, I had to search for additional data which showed more recent emissions.  I also showed a simple calculation of projected emissions assuming constant 2.1% annual emissions growth and how different emissions growth would have to be in order to achieve an emissions scenario many scientists characterize as ‘doable’: RCP4.5.

Well, a new Nature Climate Change paper (26Feb2014) updates the 2013 graph I showed, with some small changes:

 photo CO2_Emissions_AR5_Obs_Nature_article_zps1e766d71.jpg
Figure 1. Historical (black dots) and projected CO2 emissions from a Nature Climate Change article (subs. req’d).  Bold colored lines (red (RCP8.5), yellow (RCP4.5), green (RCP6), and blue (RCP2.6)) represent IPCC AR5 RCP-related emission scenarios.

Note that this figure shows exactly what I wrote about in my earlier post: historical emissions are tracking at or above the RCP8.5 scenario.  They also exceed the other three scenarios so far in the early 21st century.  These differences are relatively small so far (they will grow with time), but the trend difference between historical and RCP2.6 is already important.  As the figure shows, if we wanted to match RCP2.6 (and keep 2100 global mean annual temperatures near 2C above pre-industrial), emissions would have to be declining for multiple years already.  They aren’t.  Our actual annual emissions already exceed the annual maximum assumed by RCP2.6.  If we were to match RCP2.6 at some time in the future, emission reductions would have to be larger than RCP2.6 assumes, which is currently technologically impossible.

The figure also shows that if we continue at or along the RCP8.5 pathway, we will exceed the 2°C policy target by approximately 2046.  The paper begins with this short and sweet abstract:

It is time to acknowledge that global average temperatures are likely to rise above the 2 °C policy target and consider how that deeply troubling prospect should affect priorities for communicating and managing the risks of a dangerously warming climate.

And it includes this well-written paragraph:

This global temperature target has brought a valuable focus to international climate negotiations, motivating commitment to emissions reductions from several nations. But a policy narrative that continues to frame this target as the sole metric of success or failure to constrain climate change risk is now itself becoming dangerous, because it ill-prepares society to confront and manage the risks of a world that is increasingly likely to experience warming well in excess of 2°C this century.

I wouldn’t have used the term `dangerous` because it conveys a judgmental aspect to an objective statement.  But that’s personal style.  I agree completely with the underlying message.  If we have a small (I would say nearly zero) chance of keeping warming below 2°C this century, then 2°C shouldn’t be the target.  We can make an infinite number of possible targets, but most of them will be unachievable.  How much effort should we put into such targets?  How supportive of additional climate policies will the public be if initial targets fail early?  These aren’t simply academic questions.  Many climate activists think they’re convinced of how important action is, but their rhetoric doesn’t support that conviction.  They’re more ideological than they’d care to admit.

I met someone at a talk at the University of Colorado on Monday and ended up having lunch with them to exchange economic information for climate information.  I tried to convince them of the need to switch targets now, to no avail.  I ran into a basic problem of climate communication.  This person has a worldview and I was in the unenviable position of trying to modify that worldview.  Just as many climate communicators try to do with climate skeptics.  It’s incredibly difficult to do this because you’re dealing with a lifetime of information and experience overlaying a biology that is predisposed to that very worldview.

I will continue to post about historical versus projected emission/concentration pathways.  If activists really are supportive of the objective science as they claim, I think they will eventually shift their target.  They will of course have to come to terms with what they will initially perceive as a failure.  But the faster they can do that, the sooner we can set more reasonable and achievable targets and start making headway towards mitigation.


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Guest Teaching This Week

I’m guest teaching for my adviser’s Climate Policy Implications class while they are at a conference.  Yesterday was the easier task, as the class watched most of Leonardo DiCaprio’s “11th Hour“.  Like Gore’s “Inconvenient Truth”, DiCaprio makes widespread use of catastrophic visuals in the first 2/3 of the film.  I had discussions with classmates when I took this same class and others about the effects of these visuals.  Filmmakers design them to evoke strong emotional responses from viewers, which occurs even if you know what the intent is.  Beyond that intent, the images generate unintended consequences: viewers are left overwhelmed and feel helpless, which is the exact opposite reaction for which the film is likely designed.

The film contains spoken references to the same effect: “destroy nature”, “sick” and “infected” biosphere, “climate damage”, “Revenge of Nature”, “Nature has rights”, “nobody sees beauty”, “demise”, “destruction of civilization”, climate as a “victim”, “ecological crisis”, “brink”, “devastating”, and “environment ignored”.  These phrases and analogies project a separation between humans and nature; they romanticize the mythologized purity of nature, where nothing bad ever happens until the evil of mankind is unleashed upon it.  These concepts perpetuate the mindset that the movie tries to address and change.  That’s the result of … science.  As advocates of science, the interviewees in the film should support scientific results.  But they ignore critical social science findings of psychological responses to framing and imagery.  Why?  Because they’re locked into a tribal mindset and don’t critically analyze their own belief system.  All the while knocking the skeptics who don’t either.  I stopped using catastrophic language once I learned about these important scientific results.  The best I can do is advocate that these students do the same.

We didn’t finish watching the film during class, but the last handful of minutes we did watch did something few environmental-related films manage: stories of action and opportunity.  Filmmakers and climate activists need to stuff their efforts with these pieces, not pieces of destruction and hopelessness.  If you want to change the culture and mindset of society, you have to change your message.

Tomorrow, we’ll discuss the 11th Hour as well as this video: http://www.imdb.com/title/tt0492931/.  I also want to talk to the class (mostly undergraduate seniors, a couple of graduate students) about the scope of GHG emissions.  I’ve graded a few weeks’ worth of their homework essays and see clear parallels to the type of essays I wrote before I took additional graduate level science policy classes.  As my last post stated, too many scientists and activists get caught up using shorthand terms they really don’t understand (I should know, I used to do it too).  What does 400 ppm mean? 8.5 W/m^2?  2C warming?  Many of my science policy classes required translating these shorthand terms to units we can more intuitively grasp: number of renewable power plants required to reduce emissions to targets by certain dates.

My hope is that resetting the frame might elicit a different kind of conversation that what they’ve had so far this semester.  I also really enjoy talking about these topics with folks, so tomorrow should be fun.


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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):

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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).

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:

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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 (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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California’s Ongoing Drought & Related Climate News

California’s drought is severe and lengthy.  2013 was a record dry year for areas in the state with extensive data records: Los Angeles’s 3.60″ (14.93″ normal) and San Francisco’s 5.59″ (23.65″ normal) among others.  Recent research characterized California as drier than at any time in the past 500 years (an important point that I’ll return to below).  California experienced three consecutive very dry years (2011-2013), and 2014 provided little difference so far.  This dryness and the ensuing drought conditions are part of a longer term decadal-plus drought affecting the southwest US since 2000.

Additional metrics include:

Seventeen rural communities in California are in danger of running out of water within 60 to 120 days, according to a list compiled by state officials. As the drought goes on, more communities are likely to be added to the list.

With only about seven inches of rain in California in 2013 — far below the average of 22 inches — wells are running dry and many reservoirs are about 30 percent full (including Folsom Lake, shown above).

The Sierra snowpack, where California gets about a third of its water, was 88 percent below average as of Jan. 30.

Soon, people will face a lack of fresh water to their homes.  With reservoirs at record low levels, farmers will not be able to plant the crops they want which will reduce our food availability and increase food prices later this year.  This means the impacts will be local and national.  Moving forward, legal fights over very limited water will likely occur.  Folks are about to find out they water they’ve taken for granted is legally obligated to other users.  No one knows what the results will be, but many people have feared this very set of circumstances for a long time.

It would take between 8″ and 16″ of liquid water across most of California to break the drought.  That is unlikely to happen any time soon.  California’s drought is directly related to the snowy winter the eastern half of the nation experienced due to the persistent high-amplitude anomalous jet stream.  High pressure pushed the jet stream to the north over the western US while low pressure allowed the jet stream to dive south over the eastern US.  Usually such a pattern breaks down after a short time.  This winter’s jet stream has been essentially stuck for months now.

In related news, Arctic albedo decreased more than previously thought due to melting Arctic sea ice.  This phenomenon warms the Arctic, including the Arctic Ocean, which affects other parts of the globe, including the US.

And now back to the interesting point I wrote about above: CA is drier than at any point in the past 500 years.  Not forever, 500 years.  That means CA has been this dry in the past (the relatively recent past, in geologic time scales).  Moreover, we should all recall that CO2 concentrations were much lower 500 years ago than they are today.  That means that CA’s dryness is to some extent caused by natural variability.  The scientific question then becomes: “How much?”  Climate attribution studies remain at the forefront of climate research, which is another way of saying we don’t know how much natural variability plays a role in today’s dryness.

A NY Times article captured this recently:

While a trend of increasing drought that may be linked to global warming has been documented in some regions, including parts of the Mediterranean and in the Southwestern United States, there is no scientific consensus yet that it is a worldwide phenomenon. Nor is there definitive evidence that it is causing California’s problems.

The article notes that there are significant similarities between this drought and a similar drought in 1976-77.  What we do know is that temperatures are higher during this drought than they were in 1976-77, which exacerbates the drought’s effects.  What precipitation fell in 2013 evaporated more quickly than before because of warmer temperatures.  So we can say that a similar drought is occurring in a warmer environment, which is something relatively new and noteworthy.

An important point is that this drought is occurring in a world with higher CO2 concentrations than in 1976 or in the 1500s.  But this drought is similar to previous droughts.  Today’s higher CO2 concentrations aren’t the dominant cause of this drought.  Droughts later this century will likely have a more noticeable human fingerprint, but this drought could have (and did) occur in contemporary history.  There is nothing about today’s state of the climate (or 1970′s or 1930′s state of the climate) that precludes this drought.  Quite the opposite is true: this drought belongs to the state of the climate today, not tomorrow.

It is true that the southwest has been in some level of drought condition for 15 years or so.  Those conditions also exist in today’s climate.  They might also exist in the end of the century’s climate, but they will exhibit characteristics that we can’t foresee with any accuracy today.  That said, there are people today in the southwest US that this drought impacts.  That is the reality regardless of the anthropogenic or natural influence on the climate system.  The demand on annual available water now exceeds the supply.  That reality will increasingly shape the southwest in the near future, not the distant future.  Increasingly restrictive water usage policies are more likely than not.


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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:

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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:

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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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