Climate Change Models Are 'Dangerously Optimistic'

UK climate scientist Kevin Anderson warns that computer models predicting future climate change are underestimating emissions and overestimating technology

by Nadya Anscombe
Environment Research Web, February 24, 20011

Integrated assessment models (IAMs) used by researchers today – where climate change data is integrated with economic data – are dangerously flawed because they are based on naïve assumptions, according to Kevin Anderson from the Tyndall Centre for Climate Change at the University of Manchester, UK.

Anderson told environmentalresearchweb: “The vast majority of IAMs assume low emission growth rates; early emission peaks; annual reduction rates limited to between 2 and 4%; untested geoengineering; and a high penetration of nuclear power alongside untested ‘carbon capture and storage’ technologies. Because IAMs typically use similar and inappropriate sets of assumptions, they repeatedly come up with the same narrow and fundamentally flawed answers.”

Anderson argues that actual emissions growth rates are much higher than those used by most IAMs, and that even ambitious emission peaks are much nearer 2020–2030 than the naïve estimates of 2010–2016 used by most models. His calculations have shown that, if we want to aim for a high chance of not exceeding a 2°C increase in global temperature by the end of the century, our energy emissions need to be cut by nearer 10% annually rather than the 2–4% that economists say is possible with a growing economy.

“The output from today’s models is politically palatable,” said Anderson. “The reality is far more depressing, but many scientists are too afraid to stand up and speak out for fear of being ridiculed. Our job is not to be liked but to give a raw and dispassionate assessment of the scale of the challenge faced by the global community.” In a recent paper in Philosophical Transactions, Anderson and his colleague Alice Bows of the Sustainable Consumption Institute at the University of Manchester warn that “there is now little to no chance of maintaining the rise in global mean surface temperature at below 2°C, despite repeated high-level statements to the contrary”.

This, they say, is because of a lack of contextual thinking. For example, Anderson and Bows found that several models assumed that fossil-fuel carbon-dioxide emissions from developing nations would exceed those from industrialised nations as late as 2013–2025, despite the actual date being around 2006.

“Too many models use an extrapolation of old data and this gives results that are too optimistic,” said Anderson. “When I present my findings I am often pulled apart for taking away people’s hope. But what these models are giving us is false hope. Surely that is worse?”

He believes that this false hope that the output from these models has been spreading is one reason why policymakers and the general public have not engaged with the sweeping changes necessary for industrialised nations to drastically reduce their emissions. “This requires radical changes in behaviour, particularly from those of us with very high energy consumption,” said Anderson. “But as long as the scientists continue to spread the message that we will be ok if we all make a few small changes, then climate change will never be on top of the policy agenda and we will fail to meet our international commitments to avoid a 2°C rise.”

He adds: “All too often, climate change is described as a problem of the future, but climate change is a cumulative problem that needs to be tackled now. And this can only be done if researchers use realistic data and report brutally honest results, no matter how disturbing or depressing.”