As attacks against climate scientists have intensified, the scientific community, which usually prefers to stay far away from political controversy, has started to fight back.

Amidst the polarizing debate, some leading scientists involved in climate change studies spoke up at a May 11 Capitol Hill briefing about the knowns and unknowns in climate science.

Warren Washington

Warren Washington is former head of climate change research for the National Center for Atmospheric Research (Boulder, CO). He has been working in climate research for the past 35 years.  Washington emphasized the difference between new scientific evidence that may reveal some flaw in current understanding of climate change, and blind skepticism.

“Skepticism without specifics or alternate hypotheses or facts is worthless. It’s not really advancing the science,” Washington said.

Washington was joined in the briefing, entitled “Climate Science – Key Questions and Answers”, by Richard Smith, a professor of statistics at the University of North Carolina at Chapel Hill, and Richard Alley, a professor in the Department of Geosciences at Pennsylvania State University. (Each of the three panelists made the point that he was speaking for himself and not the institution he works for.)

AAAS, AGU, and 11 other scientific organizations offered the briefing to make it clear to legislators or their staff members, who were presumably in the audience, what is well-established scientific knowledge about climate change, and where uncertainties remain. The scientists who spoke also highlighted some steps the scientific community is taking to make the scientific process more transparent and better at avoiding errors.

Richard Smith

Richard Smith agreed with Washington that climate change skeptics with sound scientific results need to formally enter the scientific discussion.

Upon closer inspection, most skeptics’ findings would fall apart against the full weight of the scientific literature, said Smith.  But challenging results that are published in scientific journals will contribute to the field, so climate skeptics should not resort to blogs or other unofficial outlets for presenting research findings.

Smith said he regards climate scientists as extraordinarily open about making their data publicly available. He also said there’s room for improvement —for instance, by doing a better job of providing raw data so that other scientists can double-check their work.

Even in this, there are hurdles to overcome. For example, in climate research, some of the data sets can take up petabytes (millions of billions of bytes) or even exabytes (millions of trillion of bytes) of storage—a hefty technical challenge for anyone trying to share that much information. (Just one exabyte is enough to fill four million home-computer hard drives.)

Richard Alley

Richard Alley boiled down what is well known by scientists regarding climate change into a quick summary.

Citing multiple lines of evidence as he went along, Alley said “we have high scientific confidence that we are raising CO₂, and that this primarily comes from our burning of fossil fuels… CO₂ is rising, it is blocking the radiation going out to space. That’s trapped energy, and that leads to warming.”

The lines of evidence range from ice cores and satellite measurements to glacier recession and sea temperature measurements. Alley said we are already starting to see the effects of climate change.

“Various groups… have reached the same conclusion, which is that there is warming,” he said.

Conversations uncovered in hacked emails of climate researchers at the University of East Anglia do nothing to degrade our firm understanding of the science, he added.

“The results do not depend on one fact, one data set, one investigator, one anything.”

Alley added that the evidence for human induced climate change doesn’t just depend on the known effects of CO₂ and other greenhouse gases – it also relies on what scientists have been able to rule out.

“We, the whole climate community, have been spending 30 years trying to find a way out of this. Could the sun be doing it? Could the volcanoes be doing it? Could the cosmic rays be doing it?” said Alley.

“We can’t find anything else.”

The panelists’ slideshow presentations can be accessed below:

Warren Washington

Richard Alley

Richard Smith

– Colin Schultz, AGU science writer