Yes, Humans Are Causing Warming. No, We Don’t Know What That Means
Scientists are “95 percent” sure that humans are the main cause of recent global warming (up from 90 percent in 2007), but they’re much less confident about what the effects of that warming will be. That’s according to information leaked to Reuters from an upcoming report by the Intergovernmental Panel on Climate Change (IPCC).
The IPCC’s new Assessment Report (AR5), considered by many to be the definitive encapsulation of our current understanding of the planet’s climate and humanity’s role in shaping it, is scheduled to be released in October 2014. Over the next 14 months, three drafts of the report will be disseminated, the first of which is expected in the coming weeks. The last IPCC report, AR4, was mired in controversy due to a series of factual errors. This latest leaked information gives a peak at the panel’s strategy following its fall from grace in 2010: Shore up what we do know, and walk back the speculation on what we don’t.
The greenhouse gas effect is fairly simple to wrap one’s head around: certain gases trap the sun’s heat, and the main culprit, carbon dioxide, is something humans are responsible for emitting in vast quantities in recent decades. What is less clear is the degree (no pun intended) to which carbon emissions lead to temperature rise, something known as our climate’s carbon sensitivity. Our best climate models failed to predict a recent plateauing in temperatures over the past decade, despite record amounts of anthropogenic greenhouse gas emissions. We still don’t understand the ins and outs of our climate and the various feedback loops contained therein. As Reutersreports, it looks like the IPCC is finally delineating between these two issues:
“We have got quite a bit more certain that climate change…is largely manmade,” said Reto Knutti, a professor at the Swiss Federal Institute of Technology in Zurich. “We’re less certain than many would hope about the local impacts.”
And gauging how warming would affect nature, from crops to fish stocks, was also proving hard since it goes far beyond physics. “You can’t write an equation for a tree,” he said.
Once the IPCC releases AR5, scientists will hand off the baton to the policymakers. The case for dramatic action of the kind the global green set has tried and failed to secure for years now will be harder to make if the IPCC admits to greater uncertainty about local effects of warming. The green unicorn hunters will lose the most magical bow in their quiver: fear-mongering in the name of science.
That’s for the best. The more that politically impossible policy ideas fade into the background, the greater the chances that saner voices will be heard, and the more likely it is that the low-hanging fruits will be plucked—policies like telework and energy efficiency, to name just a couple. Greens have been woefully ineffective as policy advocates, but if this sneak preview is an accurate representation of what’s to come in the next IPCC report, they could be getting a much-needed opportunity to hit the reset button.