05/13/11 12:00pm

Article By: Joseph Romm

“The number of days per year in which temperatures are projected to exceed 100°F by late this century compared to the 1960s and 1970s” on our current (high) emissions path, A1FI

Last May, the U.S. National Academy of Sciences released the first of its “America’s Climate Choices” reports (see NAS labels as “settled facts” that “the Earth system is warming and that much of this warming is very likely due to human activities”).  Today, they released their final ACC report.

The good news is that the Academy is clear about the need to start reducing greenhouse gas emissions “as soon as possible” (for some reason the acronym, ASAP, sounds stronger).   The AP story got that message:  “Panel Says US Must Act Now to Curb Global Warming.”

The bad news is that the report is otherwise rather bland and conservative in that classic NAS style.  If your house were on fire, the NAS would take three months to write a report that says you should put out the fire “as soon as possible” (and, of course, you should do some adaptation planning for the potential loss of your home).

Dr. Kevin Trenberth, head of NCAR’s Climate Analysis Section, wrote in an email that, while he agrees generally with the findings, “my quick summary is that there is a lot here that is good but it doesn’t seem to go far enough.”

The NAS also makes a mistake that is emblematic of its conservative approach, as we will see.

The main flaw of this report (like all the IPCC reports) is that the authors simply refuse to clearly spell out what is likely to happen if we stay anywhere near our current emissions path — or if we only moderate our emissions but the carbon-cycle feedbacks turn out to be more serious than the models say.  The latter is a near-certainty since the models ignore most of the major decadal feedbacks, including the defrosting ‘perma’-frost (see NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100).

The report does include the figure above, which reveals that if we don’t get our act together soon, then sometime in the second half of this century most of the South will probably see summers that rarely drop below 100°F.  But the 2009 NOAA-led report on U.S. climate impacts — the source of that figure — was blunter.  And while the NAS cites that report, it doesn’t bother to review the extensive literature from the last two years on what the U.S. Southwest faces (see “USGS on Dust-Bowlification” and “NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path“).

In terms of an overall assessment of the report, it’s hard to say whether the glass is half full or half empty.  Of course nobody who matters in this town was going to drink from this cup of scientific knowledge anyway, certainly not the way the NAS was going to frame it (see WashPost: “The GOP’s climate-change denial may be its most harmful delusion”).  So you might say for the lessons in the report, the class is half empty.

The discussion of future impacts — the empty part of the cup of knowledge — is, well, almost too empty to bother reporting.  You will learn things like (p. 20):

“The IPCC’s assessment of future climate change projects that Earth’s average surface temperature will increase (in the absence of new emissions mitigation policies) between 2.0 and 11.5°F (1.1 to 6.4°C) by the end of the 21st century, relative to the average global surface temperature during 1980-1999.”

Wait. Stop the presses.  That is somewhere between untrue and exceedingly misleading.  The low end of 1.1°C warming by 2100 is in fact the low sensitivity end of the B1 scenario, which is stabilization at 550 ppm (see here).  Now technically the IPCC scenarios don’t model mitigation policies, but they effectively assume changes that require massive mitigation.  For instance, 550 ppm would probably require some 10 wedges — which is a staggering amount of clean energy deployment beyond business as usual (see “The full global warming solution: How the world can stabilize at 350 to 450 ppm“).

Indeed, the IPCC’s Special Report on Emission Scenarios (SRES) makes clear that while the SRES scenarios don’t technically have climate policies, they can and do have energy efficiency and decarbonization policies, which are the same thing.  Here’s what the IPCC says about the B1 scenario, which includes aggressive policies to limit total global warming:

Incentive systems, combined with advances in international institutions, permit the rapid diffusion of cleaner technology…. Land use is managed carefully…. Cities are compact and designed for public and non-motorized transport…. Strong incentives for low-input, low-impact agriculture. These proactive local and regional environmental measures and policies also lead to relatively low GHG emissions, even in the absence of explicit interventions to mitigate climate change.

So it is really absurd to say that the IPCC projects the Earth’s average surface temperature might increase as little as 1.1°C by 2100 “in the absence of new emissions mitigation policies.”

The more I think about it, the more problematic an error this seems to me because, again, it leaves the misimpression there is some plausible chance that, absent serious policies, we might have very little warming this century.  That sentence should not have gotten through a process reviewed by so many distinguished scientists.

This is neither an academic matter nor is it obscure.  Heck an excellent explanation of this matter is even hiding in plain sight in the Wikipedia’s entry on the IPCC emissions scenarios:

In a report published by the MIT Joint Program on the Science and Policy of Global Change, Webster et al. (2008) compared the SRES scenarios with their own “no policy” scenario. Their no-policy scenario assumes that in the future, the world does nothing to limit greenhouse gas emissions. They found that most of the SRES scenarios were outside of the 90% probability range of their no-policy scenario (Webster et al., 2008, p. 1). Most of the SRES scenarios were consistent with efforts to stabilize greenhouse gas concentrations in the atmosphere. Webster et al. (2008, p. 54) noted that the SRES scenarios were designed to cover most of the range of future emission levels in the published scientific literature. Many such scenarios in the literature presumably assumed that future efforts would be made to stabilize greenhouse gas concentrations.

MIT’s Joint Program famously published their own analysis of the “no policy” scenario.  It ain’t pretty (see “M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F“).  Indeed while the NAS report goes on and on and on about uncertainty (and why it is no reason for delay), MIT put out a figure 2 years ago that is superior to the entire NAS report.

As Andrew Freedman explained at the time:

For the no policy scenario, the researchers concluded that there is now a nine percent chance (about one in 11 odds) that the global average surface temperature would increase by more than 7°C (12.6°F) by the end of this century, compared with only a less than one percent chance (one in 100 odds) that warming would be limited to below 3°C (5.4°F).

So the NAS should not be leaving anyone with the impression that the no-policy case (aka business as usual) leads to a plausible range of warming of 2.0 and 11.5°F.  A more realistic range would probably be something like 6 to 14°F.

In case you were wondering why we should reduce emissions ASAP, the report explains the multiple reasons:

• The faster emissions are reduced, the lower the risks posed by climate change….
• Waiting for unacceptable impacts to occur before taking action is imprudent because the effects of greenhouse gas emissions do not fully manifest themselves for decades and, once manifested, many of these changes will persist for hundreds or even thousands of years.
• The sooner that serious efforts to reduce greenhouse gas emissions proceed, the less pressure there will be to make steeper (and thus likely more expensive) emission reductions later.
• The United States and the rest of the world are currently making major investments in new energy infrastructure that will largely determine the trajectory of emissions for decades to come. Getting the relevant incentives and policies in place as soon as possible will provide crucial guidance for these investment decisions.
• In the committee’s judgment, the risks associated with doing business as usual are a much greater concern than the risks associated with engaging in strong response efforts. This is because many aspects of an “overly ambitious” policy response could be reversed if needed, through subsequent policy change; whereas adverse changes in the climate system are much more difficult (indeed, on the timescale of our lifetimes, may be impossible) to “undo.”

Yes, we are in the process of screwing up this planet for possibly a thousand years or more (see NOAA: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe and 2009 Nature Geoscience study concludes ocean dead zones “devoid of fish and seafood” are poised to expand and “remain for thousands of years”).  But hey, once you apply a proper discount rate, the net present value of the suffering of those tens of billions of people hardly matter at all.

The NAS rightly says we should “Begin mobilizing now for adaptation” since even “Aggressive emissions reductions would reduce the need for adaptation, but not eliminate it.”  One can’t argue with this recommendation:

The federal government, in collaboration with other levels of government and with other stakeholders, should immediately undertake the development of a national adaptation strategy and build durable institutions to implement that strategy and improve it over time.

But, again, it ain’t gonna happen until the US scientific community, which the NAS stands at the forefront of, figures out how to deliver its scientific message to the hear-no-evil, see-no-evil, speak-some-evil crowd (see “Conservatives oppose adaptation, too“).

The report has an adequate review of the science for those who have been sleepwalking through the last decade (or watching Fox News, which is much the same thing).  If you were wondering what the science says about the change in America’s climate, here goes:

• U.S. average air temperature increased by more than 2°F over the past 50 years, and total precipitation increased on average by about 5 percent;
• Sea level has risen along most of the U.S. coast, and sea level rise is already eroding shorelines, drowning wetlands, and threatening the built environment;
• Permafrost temperatures have increased throughout Alaska since the late 1970s, damaging roads, runways, water and sewer systems, and other infrastructure;
• There have been widespread temperature-related reductions in snowpack in the northeastern and western United States over the last 50 years, leading to changes in the seasonal timing of river runoff;
• Precipitation patterns have changed: heavy downpours have become more frequent and more intense; the frequency of drought has increased over the past 50 years in the southeastern and western United States, while the Midwest and Great Plains have seen a reduction in drought frequency; and
• The frequency of large wildfires and the length of the fire season have increased

And yet the media continues to report on record-setting wildfires and record-setting drought, and record-setting deluges without hardly a word on climate change.  I guess they don’t read NAS reports, either.

The one other interesting tidbit I found was in the section on geoengineering:

Geoengineering, applied to climate change, refers to deliberate, large-scale manipulations of the Earth’s environment intended to offset some of the harmful consequences of GHG emissions, and it encompasses two very different types of strategies: solar radiation management and post-emission GHG management…..

Solar radiation management (SRM) involves increasing the reflection of incoming solar radiation back into space….  A much-discussed example is the proposal to continuously inject large quantities  of small reflective particles (aerosols) into the stratosphere….

The potential benefits of many SRM strategies are offset by potential risks. In the case of aerosol injection strategies, for example, significant regional or global effects on precipitation patterns could occur, potentially placing food and water supplies at risk. SRM alone would also do nothing to slow ocean acidification, since CO2 concentrations in the atmosphere and ocean would continue to rise. Thus, it is unclear if any of the proposed large-scale SRM strategies could actually reduce the overall risk associated with human-induced climate change.

Precisely (see Science Sunday: “The economics (or lack thereof) of aerosol geoengineering”).

Bottom Line:  This would be a good report had it been written, say, 5 or 10 years ago.  Now it is just a glass half full.  For a class that is half full.

This is a cross-post from Climate Progress.

Dr. Joseph Romm is the editor of Climate Progress and a Senior Fellow at the Center for American Progress. 

Original Post: http://climateprogress.org/2011/05/12/national-academy-america’s-climate-choices/