Carolyn Gramling writes:

The grim reality of climate change grabbed center stage in 2018.

This is the year we learned that the 2015 Paris Agreement on global warming won’t be enough to forestall significant impacts of climate change. And a new field of research explicitly attributed some extreme weather events to human-caused climate change. This one-two punch made it clear that climate change isn’t just something to worry about in the coming decades. It’s already here.

This looming problem was apparent three years ago when nearly all of the world’s nations agreed to cut greenhouse gas emissions to limit global warming to no more than 2 degrees Celsius over preindustrial times by 2100. That pact was hard-won, but even then, some scientists sounded a note of caution: That target wouldn’t be stringent enough to prevent major changes.

So the United Nations took an unprecedented step. It commissioned the Intergovernmental Panel on Climate Change to examine how the world might fare if global warming were limited to 1.5 degrees instead of 2 degrees. That report, released in October, confirmed that half a degree can indeed make a world of difference. A half degree less warming means less sea level rise, fewer species lost due to vanished habitats and fewer life-threatening heat, drought and precipitation extremes.

There’s little time to reverse course. The IPCC report notes that the planet’s average temperature has already increased by nearly 1 degree since preindustrial times, and that rise is contributing to extinctions, lower crop yields and more frequent wildfires. At the end of 2017, three attribution studies for the first time determined that certain extreme events, including an extended marine heat wave in the Pacific Ocean known as “the Blob,” would not have happened without human-induced climate change. [Continue reading…]