Scientists understate climate change impacts

Print Friendly, PDF & Email

New scientific findings are more than 20 times likely to show that global climate disruption is “worse than previously expected” rather than “not as bad as previously expected”

by Douglas Fischer
Daily Climate, October 18, 2011

The warnings were dire: 188 predictions showing that climate-induced changes to the environment would put 7 percent of all plant and animal species on the globe – one out of every 14 critters – at risk of extinction.

Predictions like these have earned climate scientists the obloquy from critics for being “alarmist” – dismissed for using inflated descriptions of doom and destruction to push for action, more grant money or a global government.

But as the impacts of climate change become apparent, many predictions are proving to underplay the actual impacts. Reality, in many instances, is proving to be far worse than most scientists expected.

“We’re seeing mounting evidence now that the scientific community, rather than overstating the claim or being alarmist, is the opposite,” said Naomi Oreskes, a science historian with the University of California, San Diego. “Scientists have been quite conservative … in a lot of important and different areas.”

Biased science

A decade ago scientists predicted the Arctic wouldn’t be ice-free in summer until 2100. But the extent of summer ice in the North has rapidly shrunk and today covers 70 percent of the area it did in 1979. Now some scientists think the Arctic could be naught but open water within 25 years.

In August, a team lead by University of York researcher Chris Thomas published a study showing that plants and animals are moving to higher elevations twice as fast as predicted in response to rising temperatures. They’re migrating north three times faster than expected, they found

As for extinctions, earlier this year two scientists at the University of Exeter paired predicted versus observed annihilation rates. The real-world rates are more than double what the best computer modeling showed: While the studies, on average, warned of a 7 percent extinction rate, field observations suggested the rate was closer to 15 percent.

Oreskes has spent a career studying climate science. She finds ample evidence that climate scientists are indeed biased – just not in the way portrayed by politicians such as Texas Gov. Rick Perry, who claimed scientists paint a bleak picture to secure more research funding.

In reality, Oreskes said, scientists skew their results away from worst-case, doomsday scenarios. “Many people in the scientific community have felt that it’s important to be conservative – that it protects your credibility,” she said. “There’s a low-end bias. It has led scientists to understate, rather than overstate, the impacts.”

Media’s fault, too

Not all scientists agree that they and their colleagues have deliberately downplayed impacts, of course.

But other scholars have noted the misperception – and argued the fault lies not just with scientists, but also with journalists reporting those findings.

In a notable 2010 study, the late William Freudenberg, a University of California, Santa Barbara, researcher who studied science and the media, found that new scientific findings are more than 20 times likely to show that global climate disruption is “worse than previously expected” rather than “not as bad as previously expected.”

He drew two conclusions from the assessment, one for scientists and one for journalists:

Scientists should be more skeptical toward supposed “good news” on global warming. And reporters, he warned, “need to learn that, if they wish to discuss ‘both sides’ of the climate issue, the scientifically legitimate ‘other side’ is that, if anything, global climate disruption is likely to be significantly worse than has been suggested in scientific consensus estimates to date.”

Inherent challenges

Of course, the science of climate modeling itself could be inherently biased. Predicting the future impact of emissions remains a difficult task, despite advances in the field over recent decades. Disparate elements can interact in surprising and additive ways that belie scientists’ best assumptions.

That may be the case with the discrepancy between predicted and observed extinction rates, said Ilya Maclean, a researcher at the University of Exeter and lead author of the study, published in July in the journal Proceedings of the National Academy of Sciences.

Many studies he examined tie predicted extinction rates to just one factor – rising temperatures, say, or loss of habitat due to sea-level rise. But a changing climate can impact habitats and species in diverse and unexpected ways, he said.

“That’s not to say there are always additive effects,” Maclean said. “But that might be one of the reasons why predictions tend to be quite conservative.”

As for the notion that scientists are – unconsciously or not – underplaying impacts, the charge has a ring of truth for Maclean.

Academics are a cautious lot, generally wary of being seen as making “alarmist” predictions, he said. The peer-review process tends to discourage bold or aggressive interpretations of data.

It’s a trend he recognizes even in his work: Maclean and his co-author, Robert Wilson, also a researcher at the University of Exeter, were careful to exclude any studies and factors they could not definitively link to climate change. That meant excluding a “fairly large” body of work from their analysis, he said.

Their standards, he acknowledges, were probably a little too conservative. But the main point of the paper wasn’t to highlight the gap between predictions and observations, he said. They simply wished to show the predictions were reasonable, not alarmist.

In an interview, Maclean was willing to “go beyond the message of the paper” and flatly state that the extinction predictions are too conservative.

But, he added, “I can’t say it definitively.”


  • On a related note, readers may want to check out this (longish) recent post on my blog —

    “Scientists struggle to motivate US politicians and public to act on climate change” at

    This is a case study of two US climate scientists who have struggled for more than 4 years to win support from politicians and the general public for their innovative proposal to mitigate CO2 emissions.

    It’s not that these researchers aren’t trying to communicate impacts and motivate policy makers to action; it’s just that there are any number of factors that complicate the communication/motivation process, not the least of which is the US public’s deplorable scientific illiteracy.

  • I think it’s high time that climate scientists conducted their own version of ‘Occupy’. They need to protest physically en masse in public until people start to take them seriously. Or at least until public opinion can be swayed to the point where denialism is back where it belongs – back with healthy and honest scientifically-QUALIFIED sceptics who continue to push science to refine its results and predictions.

    Only then might we be able to force politics to put climate change at the top of the agenda along with the need to entirely reform the political/economic system.