By Michael E. Mann

As the mercury rose in 2014, so did reasons to be thankful.

Climate change is the kind of thing that makes you feel plenty of emotions, but usually gratitude is not one of them. This year, though, something is different. Though there have been plenty of record-hot months this year, there have been even more reasons to be thankful.

2014 will likely go down as the hottest year on record, while the last decade was the hottest our thermometers have ever recorded. In this year alone, June, August, September, and October saw record-breaking heat. The year to date has been so hot that even with the recent cold snap in the United States, it is nearly certain that 2014 will go down as the hottest year on record. To avoid the record, we would need to experience the first cooler-than-average month in nearly 30 years.

Yet I find myself thankful for this hot year.

Past changes in global climate have taken place over thousands of years. Now, humans are emitting so much carbon into the atmosphere that our climate is changing at a rate that is potentially unprecedented in millions of years. As far back as the paleoclimate record takes us, we find no evidence for a warming of the globe as rapid as what we are currently experiencing.

But still, I am thankful.

While this was the hottest year on record, it should also go down as a record year for climate action. At a minimum, it will be considered a turning point: a time when the scientific evidence became crystal clear to all but the most vociferous of climate-change deniers, and industry's arguments for inaction became exhausted - even Exxon recognizes the inevitability of a price on carbon.

2014 will be seen as pivotal, when public apathy was overcome by 400,000 marchers in New York City and more across the globe, when political action started with President Obama's support for the Clean Power Plan. It will be remembered as the point at which the diplomatic climate changed, when we crossed a societal tipping point as the United States and China agreed to a partnership on reducing emissions.

Finally, in Lima this month, United Nations negotiators will craft the first draft of an agreement to be signed in Paris next year. Hopefully, this will be a strong agreement, but even a relatively weak one will be a change from constant domestic stonewalling against international climate cooperation.

Past changes in climate occurred naturally, allowing ample time for species to adapt and adjust, but current changes are occurring far too quickly for us - or other living things - to adapt to the negative impacts that could be in store, impacts on food, water, conflict, and the habitability of our environment.

I'm still thankful, though. While this is a frightening time, the rapid pace of change seems to mean that the changes are happening quickly enough for humanity to take notice and take action.

Scientists and those helping to communicate their findings have spent decades warning the public and policymakers about the climate-change threat. Meanwhile, economists and entrepreneurs have offered plausible scenarios illuminating the pathways to a clean-energy economy.

So while the Intergovernmental Panel on Climate Change released its latest series of reports over the past year documenting the changes in climate we've caused so far and the enormous cost of continued inaction, innovators like Elon Musk were busy advancing electric-car technology (it took the unprecedented step of releasing Tesla's patents for free use). While the U.S. National Climate Assessment detailed the potentially damaging impacts of climate change in store for each region of the United States, renewable-energy sources were dutifully competing with fossil-fuel energy and finally starting to win. 2014 will go down as the year renewables started to become just as cheap as fossil fuels.

Even with all these developments, we still need to do more to limit warming to safe levels. The science has been there for some time. Finally, the solutions are catching up. Now, it's up to world leaders in Lima to keep up their side of the bargain.

2014 may be the hottest year, but also one that's given me plenty to be thankful for. The momentum is there. Let's hope the negotiators give us all one more reason to be thankful.

Michael E. Mann is a distinguished professor of meteorology at Pennsylvania State University and author of "The Hockey Stick and the Climate Wars: Dispatches from the Front Lines." mann@psu.edu