Written evidence submitted by Judith Curry (IPC0052)

        To what extent does AR5 reflect the range of views among climate scientists?

I have written a paper entitled ‘No consensus on consensus’[1] that argues that the scientific consensus seeking process used by the IPCC has had the unintended consequence of introducing biases into the both the science and related decision making processes. Cognitive biases in the context of an institutionalized consensus building process have arguably resulted in the consensus becoming increasingly confirmed in a self-reinforcing way, to the detriment of the scientific process.

While the IPCC’s consensus approach acknowledges uncertainties, defenders of the IPCC consensus have expended considerable efforts in the ‘boundary work’ of distinguishing those qualified to contribute to the climate change consensus from those who are not.  These efforts have attempted to characterize those that disagree with the IPCC consensus as small in number, extreme, and scientifically suspect. These efforts create temptations to make illegitimate attacks on scientists whose views do not align with the consensus, and to dismiss any disagreement as politically motivated ‘denialism’.

A large number of climate scientists disagree with the views portrayed by IPCC; many of these scientists are included in desmogblog’s list[2] of almost 300 climate change deniers (my name is included on this list).  A reflection of disagreement with the ‘consensus’ is a recent survey[3] of the professional members of the American Meteorological Society that found only 52% agree that most of the warming since 1850 is anthropogenic, which is the principal tenet of the IPCC.               

        How effective is AR5 and the summary for policymakers in conveying what is meant by uncertainty in scientific terms?

I have been raising concerns since 2003 about how uncertainty surrounding climate change is evaluated and communicated. The IPCC’s efforts to consider uncertainty focus primarily on communicating uncertainty, rather than on characterizing and exploring uncertainty in a way that would be useful for risk managers and resource managers and the institutions that fund science.

In a series of three papers[4] I have argued that the characterization of uncertainty by the IPCC is inadequate and leads to overconfidence in the conclusions, particularly with regards to the IPCC statement on attribution.

Anthropogenic climate change is a proposed theory whose basic mechanism is well understood, but whose magnitude is highly uncertain owing to feedback processes. We know that climate changes naturally on decadal to century time scales, but we do not have explanations for observed historical and paleo climate variations, including the warming from 1910-1940 and the mid 20th century cooling. The competition for the theory of anthropogenic climate change is our recognized ignorance about what we don’t know about natural climate variability. The IPCC’s failure to adequately characterize uncertainty arises from neglecting to consider indeterminacy and ignorance in their assessments of confidence.

Does the AR5 address the reliability of climate models?

The recently released IPCC AR5 Summary for Policy Makers (SPM) of the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report makes the following statement:

“There is very high confidence that climate models reproduce the observed large-scale patterns and multi-decadal trends in surface temperature, especially since the mid-20th century. (AR5 SPM, p 9)

The IPCC’s own analysis seems to belie this statement, as evidenced by Figure 11.25 AR5. This figure shows that climate models have significantly over-predicted the warming effect of CO2 since 1990, a period during which CO2 increased from 335 to over 400 parts per million.  The most recent climate model simulations used in the AR5 indicate that the warming stagnation since 1998 is no longer consistent with model projections even at the 2% confidence level[5].

Uncertainties in climate models and their simulations are associated with incomplete understanding of the climate system, inadequacies of numerical solutions employed in computer models, uncertainty in model parameters and parameterizations of unresolved processes, and also uncertainty in initial conditions. Model outcome uncertainty, also referred to as prediction error, arises from the propagation of the aforementioned uncertainties through the model simulation.

The IPCC AR5 has placed high confidence on the simulations of climate models, in spite of the fact that climate models have significantly overpredicted the warming for the past two decades.

Has AR5 sufficiently explained the reasons behind the widely reported hiatus in the global surface temperature record?

Based upon early (leaked) drafts of the AR5, the IPCC did not even mention this hiatus. Apparently the IPCC was pressured by reviewers and its policy maker constituency to address this stagnation specifically.  Here is the relevant text from the final version of the AR5 Summary for Policy Makers:

“Models do not generally reproduce the observed reduction in surface warming trend over the last 10 –15 years.” (SPM AR5)

“There is medium confidence that this difference between models and observations is to a substantial degree caused by unpredictable climate variability, with possible contributions from inadequacies in the solar, volcanic, and aerosol forcings used by the models and, in some models, from too strong a response to increasing greenhouse-gas forcing.”  (SPM AR5)

The failure of the IPCC to predict this stagnation in warming is raising serious questions about whether climate models are over sensitive to increasing greenhouse gases. The IPCC’s dismissal of the stagnation as being associated with unpredictable climate variability raises the question as to what extent the warming between 1975 and 2000 can also be explained by unpredictable climate variability.

        Is the IPCC process an effective mechanism for assessing scientific knowledge? Or has it focused on providing a justification for political commitment?

I am increasingly concerned that both the climate change problem and its solution have been vastly oversimplified. I am concerned that the consensus seeking process used by the Intergovernmental Panel on Climate Change (IPCC) has introduced biases and acted to skew the science in the direction of self-confirmation. My research on understanding the dynamics of uncertainty at the climate science-policy interface has led me to question whether these dynamics are operating in a manner that is healthy for either the science or the policy process, acting to hyper-politicize both. I see a growing gap between what science is currently providing in terms of information about climate variability and change and the information desired by decision makers.

In the 1990’s, the U.S. and other nations embarked on a path to prevent dangerous anthropogenic climate change by stabilization of the concentrations of atmospheric greenhouse gases, which was codified by the 1992 UN Framework Convention on Climate Change (UNFCCC) treaty. The IPCC scientific assessments play a primary role in legitimizing national and international policies aimed at reducing greenhouse gas emissions. This objective has led to the IPCC assessments being framed around identifying anthropogenic influences on climate, dangerous environmental and socio-economic impacts of climate change, and stabilization of CO2 concentrations in the atmosphere.

At the time of establishment of the UNFCCC, there was as yet no clear signal of anthropogenic warming in the observations, as per the IPCC First Assessment Report (FAR) in 1990. It wasn’t until the IPCC’s Second Assessment Report in 1995 that a ‘discernible’ human influence on global climate was identified. The scientific support for the UNFCCC treaty was not based on observations, but rather on our theoretical understanding of the greenhouse effect and simulations from global climate models. By 2006/2007, climate change had soared to the top of the international political agenda, as a result of Hurricane Katrina, Al Gore’s An Inconvenient Truth, publication of the IPCC AR4 in 2007, and award of the Nobel Peace Prize to Al Gore and the IPCC.  There was a consensus that the science was settled, and that it clearly demanded radical policy and governmental action to substantially cut CO2 emissions.

Now, at the time of release of the AR5 in 2013, we find ourselves between the metaphorical rock and a hard place with regards to climate science and policy:

• substantial criticisms are being made of the IPCC AR5 Reports as well as of the IPCC process itself; IPCC insiders are bemoaning their loss of their scientific and political influence; and even IPCC insiders are realizing the need for a radical change
• climate models have failed to predict the recent stagnation in global surface temperature, and the IPCC has not provided a convincing explanation for this stagnation
• global CO2 emissions continue to increase at higher than expected rates and a growing realization of the infeasibility of meeting emissions targets
• failure of the UNFCCC Conference of Parties to accomplish much since 2009 beyond agreeing to establish future meetings
• European countries and Australia are backing away from their emission reductions policies as they realize their economic cost and political unpopularity
• increasing levels of shrillness on both sides of the political debate, steeped in moral panic and hyperbole

And finally:

• decision makers needing regionally specific climate change  information are being provided by the climate community with potentially misleading predictions from climate models.
• the politically charged rhetoric has contaminated academic climate research and the institutions that support climate research, so that individuals and institutions have become advocates; scientists with a perspective that is not consistent with the consensus are at best marginalized (difficult to obtain funding and get papers published by ‘gatekeeping’ journal editors) or at worst ostracized by labels of ‘denier’ or ‘heretic.[6]’ 

How and why did we land between a rock and a hard place on the climate change issue?  There are probably many contributing reasons, but the most fundamental and profound reason is arguably that both the problem and solution were vastly oversimplified back in 1990. This framing was locked in by a self-reinforcing consensus-seeking approach to the science and a ‘speaking consensus to power’ approach for decision making that pointed to only one possible course of policy action – radical emissions reductions. The climate community has worked for more than 20 years to establish a scientific consensus on anthropogenic climate change. However, the ongoing scientific consensus seeking process has had the unintended consequence of oversimplifying both the problem and its solution and hyper-politicizing both, introducing biases into the both the science and related decision making processes.

The framing of the climate change problem by the UNFCCC/IPCC and the early articulation of a preferred policy option by the UNFCCC has arguably marginalized research on broader issues surrounding climate change, and resulted in an overconfident assessment of the importance of greenhouse gases in future climate change, and stifled the development of a broader range of policy options. The result of this simplified framing of a wicked problem is that we lack the kinds of information to more broadly understand climate change and societal vulnerability. 

Short Biography

Dr. Judith Curry is Professor and Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology and President of Climate Forecast Applications Network (CFAN). Dr. Curry received a Ph.D. in atmospheric science from the University of Chicago in 1982. Prior to joining the faculty at Georgia Tech, she held faculty positions at the University of Colorado, Penn State University and Purdue University. Dr. Curry’s research interests span a variety of topics in climate; current interests include climate dynamics of the polar regions, climate feedback processes associated with clouds and sea ice, and the climate dynamics of hurricanes. She has published over 190 journal articles and is author of the books Thermodynamics of Atmospheres and Oceans and Thermodynamics, Kinetics and Microphysics of Clouds.  She is also Editor of the Encyclopedia of Atmospheric Sciences. She is a prominent public spokesperson on issues associated with the integrity of climate research, and is proprietor of the weblog Climate Etc. judithcurry.com. Dr. Curry currently serves on the NASA Advisory Council Earth Science Subcommittee and the DOE Biological and Environmental Research Advisory Committee, and has recently served on the National Academies Climate Research Committee and the Space Studies Board and the NOAA Climate Working Group. Dr. Curry is a Fellow of the American Meteorological Society, the American Association for the Advancement of Science, and the American Geophysical Union.

December 2013