Dennis Slonka's Dec. 8 Commentary piece (�Climate science will never be �settled� �) on climate change is wrong and stoops to personal accusations directed at my work and character....

UNIVERSITY PARK, Pa.

Dennis Slonka's Dec. 8 Commentary piece (�Climate science will never be �settled� �) on climate change is wrong and stoops to personal accusations directed at my work and character. Let me set the record straight.

Here�s what my fellow scientists and I know: Thermometers and satellites all point to the fact that the world is rapidly warming. Glaciers are shrinking, the ocean is heating and expanding, precipitation is falling in heavier doses, and we�re watching the Arctic icecap shrink away.

Why the rapid warming? Heat-trapping carbon dioxide in our atmosphere has increased about 40 percent since pre-industrial times. It comes from major industries that extract and burn coal and oil, as well as tropical deforestation.

Now, climate risks are staring us in the face. Warming has already caused sea levels to rise about 8 inches since the 1880s. By the time a mortgage taken out today is paid off, we�re likely to see the oceans rise about another foot. If emissions continue unabated, we could lock in even more sea-level rise by the end of the century, which would result in the inundation of major coastal cities around the world. No wonder insurance companies are getting more squeamish about risks from coastal flooding.

The good news is that local governments are taking climate science into account. The Rhode Island Coastal Resources Management Council, for instance, is integrating information about rising seas into coastal planning.

The bad news is that our national political conversation about climate change remains divorced from science. As Mr. Slonka notes, �Climate change has become a politically and emotionally charged subject.�

Tell me about it. I�ve had members of Congress call for criminal investigations of my work and hold hearings to attack my research. Once, a �concerned citizen� sent me an envelope full of white powder in the mail; thankfully, it wasn�t really anthrax.

Mr. Slonka goes on to say that �deniers� are only asking scientists to investigate whether human warming is a �significant� factor in the changes we see.

Of course it�s significant. If it wasn�t for all that extra CO2 in the atmosphere, Earth would be slightly cooling right now. Dozens of independent peer-reviewed studies have reached the same conclusion: rising temperatures and sea levels are directly related to the CO2 released into the atmosphere over the past two centuries by fossil fuel burning and other human activities.

More importantly, climate deniers aren�t asking questions in good faith. They�re persecuting researchers whose findings they don�t like.

I�ve written about my own strange encounters with climate denial in �The Hockey Stick and the Climate Wars� in the hopes that my colleagues � and the interested public � can learn from these experiences.

Indeed, attacks on scientists are nothing new. The lead industry went after Herbert Needleman, who found lead exposure impaired childhood brain development. Big Tobacco targeted public health researchers. Even the National Football League marginalized researchers who studied how players suffered from repeated concussions.

Some industry-funded groups and �think tanks� continue to smear me and pretend that my research is the linchpin of all climate science. But other scientists, who understand and have thoroughly reviewed my work, know my detractors have no idea what they�re talking about.

I finally decided to sue two groups that accused me of fraud in particularly insulting ways; contrary to Mr. Slonka�s claim that a jury had already ruled in the matter, my case is actively moving through the court system.

Despite the difficult position I find myself in in the climate debate, there is reason for hope.

Senators like Sheldon Whitehouse, D-R.I., are educating their colleagues about the mutual dangers we face from climate change.

In Virginia, where I serve on a state coastal commission, Republicans and Democrats are coming together to prepare for rising tides and more damaging storms.

More Republicans are speaking out too. Incoming Rep. Garret Graves of Louisiana told Bloomberg News, �For us to stick our heads in the sand and pretend [sea-level rise is] not happening is idiotic and it puts the lives of 2 million people who live in south Louisiana in jeopardy.�

Just last week, Rep. Chris Gibson, a New York Republican, told the National Journal, �I hope that my party � that we will come to be comfortable with this, because we have to operate in the realm of knowledge and science, and I still think we can bring forward conservative solutions to this.�

I hope more of their colleagues join them. We deserve a real debate about how to respond to climate change, not a fake one based on rejecting established science.

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Michael Mann is distinguished professor of meteorology at Pennsylvania State University and author of �The Hockey Stick and the Climate Wars: Dispatches from the Front Lines.�