The climate change debate is over. The question is: What will we do about it?

The earth's climate is changing. That isn't a theory. It's not controversial. It's a fact.

"Warming of the climate system is unequivocal," members of the Intergovernmental Panel on Climate Change found as far back as 2007.

We also know that human activity very likely has been driving that undeniable increase in global average temperature over the past 50 years or so.

More recently, that group, which has been compiling and studying climate change research since 1988, concluded that fossil fuel consumption accounts for the majority of those human-made emissions.

The group's 2012 report, "Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation," was the culmination of two years of research.

In it, they found statistically significant increases in heavy precipitation events in some regions and expressed "medium confidence" of climate-driven changes in flooding events -- partly because there's not a lot of data. While they found little evidence of increased tornadic and cyclone activities, they did find changes in where those storms are occurring. None of this is controversial or open to any serious type of debate.

Still, my inbox was stuffed with a good number of notes from readers responding to last week's climate change column with expressions of disbelief.

They called climate change a "hoax." Referred to some shadowy "global warming cabal." I asked who they figured was doing the hoaxing, and here's what I got in response:

"The earth has been warming for many thousands of years, long before I believe man had anything to do with it," one reader wrote. "We believe differently on the global warming issue based on our individual analyses," wrote another. They forwarded a column from a Forbes blogger and adjunct economics professor who belittled climate change "alarmists" without providing any scientific specifics backing up his claims. They forwarded a paper by an MIT scientist proposing that generally accepted models overstate the impact of CO2 in the earth's atmosphere.

But there's no fair fight in playing dueling experts on this issue. As Romney told Obama: You don't get to bring your own facts here.

All the serious scientific disagreement about climate change is about the details -- not if, but when. Not whether, but how much. Not should we, but how should we work to mitigate our effect on our environment.

"I understand people might wish it was junk science or wish they could just ignore it," Sen. Rob Hogg (D-Cedar Rapids) told me this week. "All I can say is this has been probably the most thoroughly studied scientific issue of our time."

So why are we so reluctant to admit it? Maybe because scientific conclusions have been such a long time in coming. Hogg, who gives frequent talks about climate change as part of a grass roots group called Iowa Climate Advocates, thinks it's also got to do with the way we think about our place in the world.

Throughout human history, nature's always been bigger than us. A given. The framework we live in. It can be hard to believe we can affect it on such a large scale.

But we can. We are. That's irrefutable.

"It's a reality. It's happening," said Hogg. "It's a huge threat and we just have to deal with it."

And by "we," Hogg means we. This might be a global issue, but it's an Iowa issue, too.

First, we need to think carefully about how we'll plan for future extreme weather events, biological changes and other likely effects of our changing climate.

Second, and equally important, we need to push for big, collective changes that will mitigate our impact on the atmosphere and help reverse the warming trend.

That's where we should be focusing our attention; that's what we need to discuss.

There is no more debating climate change. The question now is: What are we going to do about it?

Comments: (319) 339-3154; jennifer.hemmingsen @sourcemedia.net