warm

Roughly 61 million U.S. homes are warmed with natural gas, according to the Energy Information Administration.

Unable to warm themselves in the sun, these small, vole-like synapsids began burning calories to generate heat.

Ice helps cool the planet by reflecting sunlight, but darker seawater absorbs heat instead, which speeds up warming and contributes to even greater ice loss.

Former Conservative prime minister David Cameron said he was "desperately sad" to hear of Baroness Newlove's death and described her as "wonderful, warm, brave and plain speaking".

But emissions have grown much less quickly over the past decade as renewables have taken off, providing hope that the world's warming trend can still be curbed.