28 September 2013

Five Points on the IPCC Report (Wonky, Long)

Here are two reactions to the IPCC:
"The good news is our understanding of the climate system and our impact on it has improved immensely. The bad news is that the more we know, the more precarious the future looks. There's a clear message to Governments here, and the window for action is narrowing fast. If the last IPCC report was a wake up call, this one is a screaming siren." (source)
"Consider the case closed on global warming." (source)
Both of these quotes come from reactions to the February 2007 release of the IPCC's Fourth Assessment Report (and specifically the Summary for Policy Makers of its Working Group I) -- there are many more such reactions here.

The release of the IPCC's Fifth Assessment Report (again, technically the SPM of its WGI, available here in PDF) should give anyone following the climate issue a deep sense of deja vu, if not a full-on case of Groundhog Day syndrome. We have seen this all before.

At some risk of contributing to the deja vu, below I suggest 5 important points to take from the IPCC report released yesterday.

1. The core scientific understandings remain unchanged

The IPCC deserves much praise for bringing to the attention of the public and policy makers the fact that humans influence the climate system and that influence presents some risks. This message represents continuity with past reports. As George Monbiot explains:
There are no radical departures in this report from the previous assessment, published in 2007
Some have asserted that the IPCC's attention to a carbon budget (a trillion tons) represents something new. It is not. I discussed it in a 2006 book review (PDF) and a 2009 paper (PDF) and it certainly wasn't original to me. What is interesting is that the IPCC's WGI is taking some steps in the direction of the territory of IPCC WGIII, and a discussion of policy options.

Of course, in public debates some will emphasize the scarier end of the spectrum of uncertainty and others will emphasize the more benign end. The reality is the human-caused climate change is not about certainties, but risks and ignorance, a point well characterized by the late Steve Schneider more than a decade ago (source in PDF):
I readily confess a lingering frustration: uncertainties so infuse the issue of climate change that it is still impossible to rule out either mild or catastrophic outcomes, let alone provide confident probabilities for all the claims and counterclaims made about environmental problems.
The IPCC report already is being spun silly. Underneath the spin is an important core message.

2. The IPCC itself is still engaged in PR spin and messaging

The IPCC AR4 got into some trouble for its efforts to spin science beyond what it could bear. The 2035 glacier issue got the most attention, but for me it was the egregious treatment of work I have been involved in related to disasters that really caused me to question the integrity of the organization. Unfortunately, vestiges of such tactics appear to persist.

For instance, in the AR4 released in 2007, the IPCC was willing to highlight the significance of 6 years worth of global temperature data in supporting its conclusions:
Six additional years of observations since the TAR (Chapter 3) show that temperatures are continuing to warm near the surface of the planet. The annual global mean temperature for every year since the TAR has been among the 10 warmest years since the beginning of the instrumental record.
Now with global temperatures in an extended hiatus, the IPCC has reversed course and told us that such short-term periods are actually irrelevant to its arguments:
Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends. As one example, the rate of warming over the past 15 years (1998–2012; 0.05 [–0.05 to +0.15] °C per decade), which begins with a strong El NiƱo, is smaller than the rate calculated since 1951 (1951–2012; 0.12 [0.08 to 0.14] °C per decade)5. {2.4}
Back in 2006 my father and I warned against presenting too tidy a case based on an expectation of sustained surface temperature warming. (And he is on record in the scientific literature making such a case more than 10-years ago -- see this paper in PDF -- yet another subject which he has been proven right about after being first attacked, but more on that another time!).

The IPCC may be absolutely correct in its assertion that the so-called "hiatus" is of little relevance to its arguments -- no doubt we'll be hearing more about this in coming weeks and months. However, the IPCCs past willingness to spin data one way, and now another cannot build confidence in the IPCC's ability to play things straight.

Speaking for the IPCC, Princeton's Michael Oppenheimer explains that the IPCC full report, to be released next week, will comprehensively dealy with the "hiatus":
[T]he [IPCC] scientists looked at [the hiatus] very carefully. There's an extensive discussion of it in the detailed background documents will be made public on Monday.

There's been a slowdown. It hasn't stopped. The warming rate has been slower over the last 15 years than the long-term trend.

And that is believed to be because the climate is quite variable. If you look at the long-term record, there are bumps upwards, there are bumps downwards, and there are plateaus like this one. After every bump downward or every plateau, the climate change then accelerates again. Now, we can't be sure that is going to happen, but it's a good bet.

The best possible -- the best -- the leading explanation of this is that heat tends to hide in the ocean sometimes. But when heat hides in the ocean, it later comes out and reappears in the atmosphere, and then warming resumes faster than before. We don't know this for certain. We will find out over the next few years.
UPDATE 9/29: Pete Spotts reports a somewhat different account than Oppenheimer's on how the IPCC handled the "hiatus."

At the University of Nottingham, Reiner Grundmann has created word clouds of the 2007 IPCC SPM and its successor released yesterday. They show how fundamentally the IPCC has altered its emphasis.

2007 IPCC AR4 WGI SPM (source)

Word cloud made with WordItOut

2013 IPCC AR5 WGI SPM (source)

Word cloud made with WordItOut

Last week, I noted that the 2007 IPCC WGI had expressed 10 statements (in the entire report) with 95% or greater confidence. Only one of these appeared in the SPM. In the 2013 IPCC WGI SPM there are 18 such statements expressed at a 95% or greater likelihood. Whether this reflects a change in approach or a change in knowledge remains to be seem, but it is a significant difference in presentation.

Here is my bottom line: I trust the science being reported by the IPCC. I still do not trust the IPCC to faithfully report that science without trying to spin a message.

3. We will not be able to clearly distinguish the influence of that human influence from natural variability for decades:

The IPCC SPM explains:
Internal variability will continue to be a major influence on climate, particularly in the near-term and at the regional scale.
This means that there are exceedingly few variables in which human-caused climate change can be detected and attributed over the coming "short-term" (how long is that?). Apparently we can now add global surface temperatures to that list (at least over 15 years, it is not clear what the IPCC thinks is long enough, maybe we'll learn that answer in the full report).

In theory, such a conclusion should put to rest the incessant "wiggle watching" of various climate variables that goes on with respect to multi-year, yearly and even shorter time periods. Of course, in practice wiggle watching is a great pastime of the climate warriors on either side. The IPCC's (thus far) unwillingness to take head-on issues associated with the "hiatus" almost guarantees debates over the "wiggles" will continue.

The bottom line lesson to take from the IPCC is that such "wiggle watching" will be largely irrelevant to its core findings (discussed above under #1).

4. Actions to mitigate climate through reductions in carbon dioxide (and other greenhouse gases) will not have a detectable effect on climate until after mid-century.

The IPCC explains:
By the mid-21st century the magnitudes of the projected changes are substantially affected by the choice of emissions scenario.
This long time-scale of a detectable impact of mitigation can also be seen in the Table box SPM.2 where you can see that the uncertainty ranges for the temperature increase projected for 2065 for the highest and lowest emissions scenarios overlap. For sea level rise the ranges are just about identical. So under the assumption that the models can accurately predict future temperature change, even under very aggressive emissions reductions scenarios now thought unrealistic, we would not be able to conclusively see these effects in global average temperature by 2065. (Ironically, this also means that the only way we could actually verify century-long climate models against data would be to not engage in mitigation!)

This conclusion is not new (I highlighted it in 2006 testimony before the US Senate, here in PDF). The IPCC should put to rest silly claims that action on emissions, even very aggressive actions, can have a meaningful effect on short-term weather and climate. Here is a prominent example of such a claim from Al Gore eight days ago:
Three years ago, Congress failed to put a price on carbon and, in doing so, allowed global warming pollution to continue unabated. We have seen the disturbing consequences that the climate crisis has to offer—from a drought that covered 60% of our nation to Superstorm Sandy which wreaked havoc and cost the taxpayers billions, from wildfires spreading across large areas of the American West to severe flooding in cities all across our country—we have seen what happens when we fail to act. 
The asymmetry in costs and benefits of climate policy as climate policy is one of the fundamental motivations behind a Hartwellian approach to climate.

5. There is not a strong scientific basis for claiming a discernible effect of human-caused climate change on hurricanes, floods, tornadoes or drought.

This is a familiar conclusion to readers of this blog, so I won't belabor it (more to come soon on this). Here is what the IPCC SPM says about each looking out to mid-century:
  • Hurricanes (tropical cyclones):  "Low confidence" in both a "human contribution to observed changes" and "likelihood of future changes"
  • Floods: No comments in the SPM
  • Tornadoes: No comments in the SPM
  • Drought:  "Low confidence" in both a "human contribution to observed changes" and "likelihood of future changes"
The conclusions with respect to hurricanes and drought both represent a walking back from more aggressive conclusions reported in 2007, and should not be a surprise to readers here, as that is what the literature says. Kudos to the IPCC for getting this right.