A federal appeals court okayed climate scientist Michael Mann's defamation suit, finding that a reasonable jury would believe that the National Review's accusations of academic fraud, peppered with comparisons to child molesters, were baseless and harmful to his career.

As we head into an administration where harassment of scientists seems likely, a path through the courts against intimidation could prove essential. Reminds us of the time the Heartland Institute built billboards comparing climate scientists to bin Laden and the Unabomber, and promptly lost funding. 

Investors are zeroing in on the use of information known as environmental and social governance (ESG) data to identify risks that might not be captured on standard balance sheets.

One such risk is climate: none of the world's oil or gas companies disclose the potential emissions from their fossil fuel reserves even though world regulatory frameworks (and scientific reality) necessitate that a significant portion of those reserves remain in the ground. Cognizant of this, Exxon earlier this year took a huge financial hit and wrote down almost a fifth of its reserves.

Now a board of the world's bankers advising the G20 is encouraging member countries to adopt financial disclosure rules for companies to report their climate risk. Some firms are actually pretty amped about this.

In response to the possibility that Republicans may cancel funding for NASA's atmospheric sciences missions (which provide the bulk of climate data), Jerry Brown says California will "launch its own damn satellite." 

Gauging purely on the size of the California economy, they should be able to do it. Spain, with a GDP about $1 trillion lower, is set to shortly launch its first earth observation satellite. 

Reminder: California's ambitious climate leadership is now arguably the most important policy experiment underway in the United States today.

Stephen Hawking isn't wrong to say that this is the most dangerous time in our planet's history. Sure, we might nuke ourselves to oblivion before the waters finish rising, but in the long run, few threats to human existence are as certain and damaging as environmental destruction. 

So, in totally contrary form, here are some reasons to be optimistic about climate action, starting with the historic reversal of the Dakota Access Pipeline as the Army Corps of Engineers admitted it could not go on as planned. Behind their reasoning: A pipeline leak posed an unacceptable threat to drinking water for the Standing Rock Sioux. Here are the last 30 years of spills, leaks, and explosions, mapped.

While stopping the pipeline's route under the Missouri River may not prevent oil from coming to market, it's a victory for the human right to water won after the largest congregation of Native tribes in over a century (over 280). 

The next battles begin today, as Canada's first nations are appealing to Prime Minister Trudeau to reject pipelines on similar grounds.

A November court case in Oregon gave legal standing to kids organized as Our Children's Trust, and they have an outside chance to win a court-mandated, scientifically-rigorous climate plan for the United States.

It happened quietly, but the passage in October in Kigali of an international treaty to limit hydrofluorocarbons (HFCs)—which are potent greenhouse gases—should "abate global warming by up to 0.5° C." That deal went through, perhaps surprisingly, with lots of support from refrigerant companies, which is encouraging news to the climate champions who argue that America's next big steps on carbon reduction will be driven by business, not government. 

The half degree Celsius saved by Kigali could be huge, for example by spelling the difference between life and death for coral reefs. Canada has already drafted actions to draw down HFC use.