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Climate Sensitivity and 21st Century Warming

I want to write about shoddy opining today.  I will also write about tribalism and cherry-picking; all are disappointing aspects in today’s climate discussion.  In climate circles, a big kerfuffle erupted in the past week that revolves around minutiae and made worse by disinformation.  The Research Group of Norway released a press release that somebody’s research showed a climate sensitivity of ~1.9°C (1.2-2.9°C was the range around this midpoint value) due to CO2-doubling, which is lower than other published values.

Important Point #1: The work remains un-peer reviewed.  It is part of unpublished PhD work and therefore subject to change.

Moving from that context, what happened next?  The Inter-tubes were ablaze with skeptics cheering the results.  Additionally, groups like Investor’s Business Daily jumped on the “global warming is hooey” bandwagon.  Writers like Andy Revkin provided thoughtful analysis.

Important Point #2: Skeptics view some model results as truthful – those that agree with their worldview.

IBD can, of course, opine all it wants about this topic.  What obligation to their readers do they have to disclose their biases, however?  All the other science results are wrong, except this one with which they agree.  What makes the new results so correct when every other result is so absolutely wrong?  Nothing, as I show below.

Important Point #3: These preliminary results still show a sensitivity to greenhouse gas emissions, not to the sun or any other factor.

For additional context, you should ask how these results differ from other results.  What are IBD and other skeptics crowing about?

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Figure 1Distributions and ranges for climate sensitivity from different lines of evidence. The circle indicates the most likely value. The thin colored bars indicate very likely value (more than 90% probability). The thicker colored bars indicate likely values (more than 66% probability). Dashed lines indicate no robust constraint on an upper bound. The IPCC likely range (2 to 4.5°C) is indicated by the vertical light blue bar. [h/t Skeptical Science]

They’re crowing about a median value of 1.9°C in a range of 1.2-2.9°C.  If you look at Figure 1, neither the median nor the range is drastically different from other estimates.  The range is a little smaller in magnitude than what the IPCC reported in 2007.  Is it surprising that if scientists add 10 more years of observation data to climate models, a sensitivity measurement might shift?  The IPCC AR4 dealt with observations through 2000.  This latest preliminary report used observations through 2010.  What happened in the past 10 years that might shift sensitivity results?  Oh, a number of La Niñas, which are global cooling events.  Without La Niñas, the 2000s would have been warmer, which would have affected the sensitivity measurement differently.  No  mention of this breaks into the opinion piece.

Important Point #4: Climate sensitivity and long-term warming are not the same thing.

The only case in which they are the same thing is if we limit our total emissions so that CO2 concentrations are equal to CO2-doubling.  That is, if CO2 concentrations peak at 540ppm sometime in the future, the globe will likely warm no more than 1.9°C.  Note that analysis’s importance.  It brings us to:

Important Point #5: On our current and projected emissions pathway, we will more than double pre-industrial CO2 concentrations.

 photo CO2_Emissions_IPCC_Obs_2011_zpsa00aa5e8.jpg

Figure 2.  Historical emissions (IEA data – black) compared to IPCC AR4 SRES scenario projections (colored lines).

As I’ve discussed before, our historical emissions continue to track at the top of the range considered by the IPCC in the AR4 (between A2 and A1FI).  Scientists are working on the AR5 as we speak, but the framework for the upcoming report changed.  Instead of emissions, planners built Representative Concentration Pathways (RCPs) for the AR5.  A graph that shows these pathways is below.  This graph uses emissions to bridge between the AR4 and AR5.

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

Figure 3. Representative Concentration Pathways used in the upcoming AR5 through the year 2100, displayed using yearly emissions estimates.

The top line (red; RCP8.5) corresponds to the A1FI/A2 SRES scenarios.  As Figure 3 shows, our historical emissions most closely match the RCP8.5 pathway.  The concentration for this pathway through 2100 is 1370ppm CO2-eq, which results in an anomalous +8.5W/m^2 forcing.  This forcing is likely to result in 4 to 6.1°C warming by 2100.  A couple of critical points: in this scenario, emissions don’t peak in the 21st century; therefore this scenario projects additional warming in the 2100s.  I want to make absolutely clear this point: our business-as-usual concentration pathway blows past CO2-doubling this century, which means the doubling sensitivity is a moot point.  We should investigate CO2-quadrupliung.  Why?  The peak emissions and concentration, which dictates the peak anomalous forcing, which controls the peak warming we face.

The IBD article contains plenty of skeptic-speak: “Predictions of doom have turned out to be nothing more than madness”, “there are too many unknowns, too many variables”, and “nothing ever proposed would have any impact anyway”.

They do have a point with their first quoted statement.  I avoid catastrophic language because doom has not befallen the vast majority of people on this planet.  Conditions are changing, to be sure, but not drastically.  There are too many unknowns.  Most of the unknowns scientists worked on the last 10 years ended up with the opposite result that IBD assumes: scientists underestimated feedbacks and results.  Events unfolded much more quickly than previously projected.  That will continue in the near future due mainly to our lack of knowledge.  The third point is a classic: we cannot act because others will not act in concert with us.  This flies in the face of a capitalist society’s foundation.  Does IBD really believe that US innovation will not increase our competitiveness or reduce inefficiencies?  Indeed, Tim Worstall’s Forbes piece posited a significant conclusion: climate change becomes cheaper to solve if the sensitivity is lower than previously estimated.  IBD should be cheering for such a result.

Finally, when was the last time you saw the IBD latch onto one financial model and completely discard others?  Where was IBD in 2007 when the financial crisis was about to start and a handful of skeptics warned that the mortgage boom was based on flawed models?  Were they writing opinion pieces like this one?  I don’t think so.  Climate change requires serious policy consideration.  This opinion piece does nothing to materially advance that goal.


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7th Day of 100+F Heat In Denver, CO; June 2012 Hottest On Record

It’s official: June 2012 was the hottest June on record in Denver, CO (dating back to 1872) with an average temperature of 75F, 7.6F above normal!

Yesterday’s high of 101F added to the total number of days of 100F+ temperatures: to date, there are now 7.  Last week, there were 5 days in a row of 100F+ heat, matching the all-time record for Denver.  The streak included 2 105F readings, which tied for the all-time hottest temperature recorded for Denver.  There was also a 100F+ reading a few days prior to that streak.  For completeness, I want to point out that the 27th through 30th of June weren’t much cooler: it was 97, 97, 98, and 99 on those four days, so we didn’t miss 100 by much.

Here are a few pictures demonstrating the intensity and extent of the heat that not only affected Denver, but much of the High Plains prior to the impacts east of the Mississippi over the weekend:

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Figure 1. Contour plot of surface maximum temperatures for July 1, 2012.

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Figure 2. Plot of surface maximum temperatures by station for July 1, 2012.

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Figure 3. Contour plot of surface maximum temperatures for June 30, 2012.

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Figure 4. Contour plot of surface maximum temperatures for June 29, 2012.

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Figure 5. Plot of surface maximum temperatures by station for June 26, 2012.  This is one of the two dates that Denver’s temperature tied for the all-time recorded high of 105F.

Context

Last year, there were 50 consecutive days of 90F+ maximum temperatures at Denver, which tied for 9th-longest in our recorded history.  With 7 additional days, it would have been the 3rd-longest streak; 11 more days would have tied the longest streak on record, set in 2000.  Note also that 6 of the 11 longest streaks have occurred in the 21st century!  Normally, Denver experiences ~34 days of 90F+ maximum temperatures.

So far this year, we are in the middle of a 10-day streak.  Today, the temperature has already been over 90 for over 4 hours (now 2:30P local) and the forecast calls for 90F+ for at least the next 5 days.

I couldn’t find records on the average number of 100F days in Denver in a year.  I would venture a guess and say that is because the number is less than one.  I’ll do some more digging and see if I can find out one way or the other.

Climate Projections

It wasn’t that long ago that I first saw projections of potential future climate maps for the US and didn’t think I could imagine what it would be to live through such conditions.  I’m sure there are many people who either similarly couldn’t imagine it because it hasn’t happened yet or who are simply unaware of such projections.  Take a look at the following graphic:

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Figure 6. Projection for 2090-2099 of the number of weeks per year where maximum daily temperatures exceed 100F.  This projection used the A1FI SRES scenario, which best represents the globe’s current emissions path.

For the sake of conversation, I will assume that Denver has so far this year experienced 1 week (7 days) of 100F+ temperatures, and will further assume that no additional 100F days will occur in the rest of the year.  Under the A1FI scenario, by the end of this century, such a year would be considered relatively cool!

This shift toward more extreme temperatures can also be represented in this graphical manner:

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This graphic shows that the increase in average temperature does not have to be that large in magnitude in order for a sizable number of events at the tail of a distribution (e.g., temperature) to occur.

Millions of people are currently without power (due to violent thunderstorms) and are experiencing 100F+ temperatures in the eastern US.  How many more summers like this do they want to have?  They’re going to find out, that’s very nearly certain now.


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Changes In The Arctic

I’ve written about Arctic sea ice conditions for a couple of years now. As I’ve written new posts, I’ve tried to include information regarding the science behind the conditions being written.  2010 was a particularly bad year for Arctic ice, as conditions were recorded to be well below average conditions for months at a time.  Arctic ice in September 2010 challenged the record low minimum extent observed in the modern era in 2007.  My summary conclusion after paying attention to Arctic sea ice is this: the Arctic has entered into a new climatic regime.  Conditions are now regularly quite different than those observed in the past couple hundred years.  I’m going to provide a broader look at this topic in this post.

When I have written about climatic changes, especially in the context of the Intergovernmental Panel on Climate Change’s 4th Assessment Report Physical Science Basis (IPCC 4AR WG1), I have increasingly mentioned the disturbing fact that the IPCC’s projections were far too conservative to be of real use to policy makers.  The reason is both simple and complex.  Simply put, the IPCC focused on moderate greenhouse pollution scenarios that were better researched.  The biggest problem with that is the globe’s actual emissions path is following the worst-case scenario (A1FI) considered by the IPCC 4AR (courtesy of Hansen and Sato; data through 2010):

Of greater complexity is the “better researched” part of my statement.  Critical feedbacks were largely kept out of climate model runs leading up to the 4AR.  There is nothing intrinsically wrong or manipulative about this.  Those feedbacks remain less researched and therefore less understood than other processes included in state-of-the-art model efforts.  That situation is improving, as feedbacks are coming under increasing scrutiny.  This is where politics intrudes: somebody has to fund that research.  There was a strong effort during most of the past 10 years to slow down or stop this kind of climate research.  Budgetary pressures moving forward will cause potential future research to be shelved when it’s needed most.

Back to the IPCC 4AR.  One of the problems with relying on scenarios that don’t accurately reflect the true state of the climate system is projections are starting to look overly cheerful.  Take Arctic sea ice extent as an example.  From the 2009 Copenhagen Diagnosis, we can see that not only does the mean of the IPCC models over-project the extent of September Arctic sea ice only a few short years after making the projections, but the worst-case scenario wasn’t able to capture how low sea ice extent would get prior to 2010 (data through 2008); [h/t msobel for reminding me this graph existed].

September 2009’s extent was similar to 2008’s.  2010’s looked more like 2007’s, which is represented by the lowest point of the red line in the above graph.  In other words, the observations time series continues to record values substantially lower than the bottom of the IPCC models’ range.  Scientists (and others) love to ask, “Why?”  So, the question should be, “Why were the IPCC models so far off on this projection?”  A quick note: a growing number of other kinds of projections are showing similar signs of being worse than projected much sooner than was thought to be the case.  I will discuss some, but not all, of the factors involved in this phenomenon.

I’ve already shown the annual growth of CO2 emissions over the past 50 years.  That, of course, is only part of the story.  Since CO2 isn’t scrubbed from the atmosphere very quickly, CO2 concentrations have risen with that growth of CO2 emissions.  Here is the state of atmospheric CO2 concentrations measured at Mauna Loa, Hawai’i as of early February 2011:

(Courtesy Tans et al., NOAA/ESRL web site)

Up and up it goes.  2010’s average CO2 concentration was 389.69ppm.  That will be the last time in a long time that the concentration will be below 390ppm.  Today’s concentration is higher than at any point during the past few hundreds of thousands of years.  Oh yeah, I almost forgot, the last time concentrations were above 400ppm for an extended period of time (somewhere between 400 and 560ppm), the Greenland ice sheets collapsed.  That’s because there is a melting ice/warmer air feedback that occurs around Greenland.  The problem?  Nobody knows exactly where the tipping point leading to collapsing ice sheet exists.  Since we’re only 10ppm  and 5 years away form 400ppm, does anybody seriously want to continue gambling?  After all, it’s going to take quite some time to get that concentration back below 400ppm; more time will be required the longer we wait.

CO2 is being emitted into the atmosphere faster than it is being removed.  The concentration of CO2 is therefore increasing.  As a result of very basic physical laws, more and more solar energy is accumulating in Earth’s climate system.  Part of this energy is manifesting as increased surface temperatures:

This graph shows 5-year and 11-year running averages of global temperatures as analyzed by NASA’s James Hansen.  Within this data, something interesting is occurring.  And it didn’t become obvious until Hansen published a different kind of temperature anomaly graph.  Instead of averaging the entire globe’s temperatures together, Hansen averaged temperatures over different latitude bands together:

If it’s too hard to make out all the little details, check out this web page, where you can click on a PDF which shows a much larger version.  I’m going to concentrate on the top two boxes in this graph, which show temperature anomalies for five zones (upper-left) and for the two polar zones (upper-right).

The first thing I want to point out is the period between 1940 and 1980.  This period has been cited recently by climate zombies as one reason not to listen to climate scientists.  According to the zombies, predictions were made in the 1970s about global cooling.  Nothing exists in the scientific literature supporting this claim, of course.  What scientists did say in the 1970s was the recent warming trend was no longer evidenced and they wondered what could be causing it.  Without getting further into the minutiae, the top two time series show where the global signal originated from: the Arctic.  It was the zone that showed the strongest signal that looks similar to the signal seen in the global temperature anomaly time series.  Since the 1970s, the Arctic’s surface temperatures have warmed more than any other zone.  You can see that in 2010, the Arctic temperature anomaly was greater than 3.6F (2C).  The northern mid-latitudes (23.6°N to 64.2°N, or the zone in which most of us live) has “only” warmed by just under 1.8F.  The northern mid-latitudes showed a slight cooling from the mid-1960s to the mid-1970s, but if you look at the time series on the bottom-left, the scale is much smaller than the Arctic graph in the upper-right.

So that’s what’s happened in the lowest part of the atmosphere above the Arctic: the greatest warming of any zonal area on Earth since the 1880s.  Arctic sea ice, of course, rests on water – the Arctic Ocean, to be precise.  Something has been occurring to the Arctic Ocean at the same time that the atmosphere above the ice has been steadily warming.  Unfortunately, it’s the same phenomenon: water entering the Arctic from the Atlantic is warmer than it has been at any point in at least the past 2,000 years.  This water is 3.5F warmer today than it was one century ago.  It is 2.5F warmer today than it was during a favorite time period for climate zombies, the Medieval Warm Period, during which Europe warmed while most of the rest of the globe didn’t see much change.  But even if the effect was global, as they wish it was, conditions are warmer today by a substantial margin.  Not only that, but the volume of water entering the Arctic from the Atlantic has also increased over the past century.  If the same volume of water that was warmer was the situation, that would be bad enough.  But significantly more water that is significantly warmer than similar water was 100 years ago is a double whammy.  What this mean is Arctic ice has a harder time forming along the edge of the ice pack on a year-to-year and decade-to-decade basis.  This is evident in the following graphic:

(courtesy Robert F. Spielhagen, Science)

The red arrows represent flow direction of Atlantic water entering the Arctic Ocean at depth.  The white arrows represent flow direction of ice exiting the Arctic Ocean at the surface.  The solid white line represents the average sea ice coverage for April from 1989 to 1995.  The broken white line represents the average sea ice coverage for April from 1963 to 1969.

Why are the time series and study results relevant to the comparison of ice extent observations against IPCC model projections?  Because they represent only a small number of examples of how increasing understanding of the Arctic has occurred in recent years and that’s problematic when interpreting the IPCC’s results.  I haven’t covered how the warming observed in the Arctic so far is thawing permafrost both on land and underwater, which is projected to release 1 Billion tons of carbon into the atmosphere yearly by the 2030s – and how such a process likely won’t be included in the IPCC 5AR.  Additionally, most of that carbon will be released as methane, which is 72 times as efficient a greenhouse gas over a 25 year period than CO2.  I haven’t covered how the retreat of Arctic sea ice is causing additional solar energy to be collected by dark sea water instead of being reflected back into space by white ice – and how such a process also isn’t included in today’s climate models.  I haven’t covered how over 80% of the solar energy absorbed in the past couple hundred years is currently stored in the world’s oceans, mostly at depth.  When that warmer water rises to the surface, it will interact with a warmer atmosphere in ways that are not completely understood.  Of course, warmer waters means Arctic sea ice will have even less of a chance of existing year-round in tomorrow’s world.

To some extent, I have talked about the dangers involved with spending most of our research time on moderate emission/warming scenarios, when our actual emission scenario is closer to the worst-case considered in the 2007 report.  But all of the feedbacks I’ve discussed so far are lacking from all of the emission scenarios.  What will happen when those feedbacks are included?  Instead of “5.0 °F with a likely range of 3.1 to 7.9 °F” for the A1B scenario or “7.2 °F with a likely range of 4.3 to 11.5 °F” for the A1FI scenario from the 4AR by 2100, the globe could experience 10-13°F warming by 2100.  Long before then, the Arctic will likely have attained a new stable climate; one that is quite different from the climate present during most of our species’ existence.

The Arctic has entered into a new regime.  Even climate scientists are playing catch-up right now, which means the American public is way behind in understanding what changes in the Arctic mean to them.

Cross-posted at SquareState.


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2010 Warmest Year On Record, Says NASA & NOAA

The news is in and it isn’t good.  Despite a strong La Nina during the second half of the year and cold air able to escape the Arctic and affect Europe and the eastern U.S., 2010 was the warmest year since 1880.

The top-10 warmest years in the NASA record are now:

2010, 2005 (actually 0.018°F less than 2010), 1998, 2002, 2003, 2006, 2007, 2009, 2004 and 2001.

9 out of the 10 warmest years on record have now all occurred since 2002.  The 12 warmest years on record have occurred since 1997.  Global warming has not stopped.  Global warming will not stop unless and until we stop polluting the climate system with greenhouse gas emissions at a tiny fraction of our current pace.

NOAA has put together their annual global report, which acts as confirmation of the NASA result: 2010 is statistically tied with 2005 as the warmest year in their dataset.

To the climate zombies that infest the discussion over what to do about global warming, consider the following: 2010 was “only” 1.12°F (0.62°C) above the 20th century average of 59.0°F.  Our current emissions trajectory is closest to the A1FI emissions scenario in the IPCC’s SRES family.  Results of running that scenario through climate models produced the following results: best estimate temperature rise of 7.2°F with a likely range of 4.3 to 11.5°F (4.0 °C with a likely range of 2.4 to 6.4 °C).

Multiple extreme weather events also characterized 2010 and continue to do so in early 2011.  From a heat wave worse than any seen in the past few thousand years across eastern Europe and Russia that claimed many lives and spawned massive wildfires to related Pakistani floods that affected tens of millions of people to floods in Australia that cover more area than several countries in Europe, loaded die are starting to land.  The costs of these disasters already reach into the tens to hundreds of billions of dollars.  If these kinds of horrific events are already occurring with only 1.12°F warming, what will happen when the globe warms by an average of 4.3°F, 7.2°F, or even 11.5°F?  It can be summed up simply: stress will move beyond impacting disparate societies; our civilizations will be stressed to breaking points, to say nothing of ecosystems across the planet.

Cross-posted at SquareState.

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