President Trump mocked the idea of global warming in a tweet Thursday, making one of his first (if not the first) such public comments on the topic since entering the White House almost a year ago.

Why it matters: Trump has tweeted in the past that he thinks global warming is a hoax, but that was in 2012 and he has not focused on the topic much at all in his Twitter activity as president. This tweet shows he's still openly mocking mainstream climate change science, even without directly questioning it.

Fast facts: Most scientists agree human activity, primarily through the burning of fossil fuels, has been the primary contributor to Earth's aggregate temperature going up this past century. That does not mean, though, that freezing cold weather, like the East Coast is experiencing right now, won't happen in the future in many parts of the world. Climate change science is much more complicated than that, but citing cold weather is still a favorite line of politicians and others who doubt climate change is happening. Sen. James Inhofe, Republican from Oklahoma, threw a snowball on the Senate floor in February 2015 to mock global warming.

One level deeper: Trump's tweet was also mocking the Paris climate deal, a global accord virtually every country in the world except the United States supports. It calls on countries to cut greenhouse gas emissions, but as it stands the commitments wouldn't cut emissions to the levels most scientists say is needed. America's commitment under President Obama was actually relatively moderate -- up to 28% cut in such emissions by 2025 based on 2005 levels, but the Trump administration pointed to conservative groups' studies showing it could cripple the U.S. industrial economy while other countries, notably China, were called on to do less.

Between the lines: The Trump administration released without political influence a statutorily required report earlier this year confirming in great depth that human activity is driving climate change. Trump's tweets get a lot of attention, but make sure to also watch what the administration does or doesn't do on this issue.

The bottom line: Words matter, and so do the president's tweets. His perspective on this issue is influencing his most ardent followers, a new poll suggests. A survey released in October from George Mason University found that just 21% of conservative Republicans think global warming is mostly human-caused, a decrease of nine points since earlier this year.

One more thing:

The semantics around climate change, or global warming, are almost as divisive as the science itself. Global warming was the default term up until the last decade or so, when climate change became more popular among those urging action to cut greenhouse gas emissions. That shift was partly to respond to comments like Trump made Thursday by clarifying that a higher global aggregate temperature does not mean the entire planet would be getting universally warmer.