With America's headline-grabbing election barreling down on us like a freight train, the world is wondering what the next U.S. president will do to stave off climate chaos.
But as global warming accelerates, every week is a precious opportunity for action. Record-breaking heat and climate-fueled storms like Hurricane Matthew demonstrate delay's deadly cost.
President Barack Obama, fortunately, still has time to take critical new steps and secure his climate legacy. In the president's last 100 days in office, here are five ways he can curb carbon pollution, leave dirty fossil fuels in the ground, and show U.S. leadership in the global fight for climate justice.
1.Put America's public lands off limits to new drilling and fracking
To preserve a livable planet, we must keep most fossil fuels in the ground.
That's why President Obama should halt all new federal fossil-fuel leasing on America's public lands and in our oceans. That could keep 450 billion tons of climate pollution in the ground. And the president can stop the senseless sale of these publicly owned resources now -- under existing U.S. law -- without action by Congress.
The Obama administration has already implemented a moratorium on new coal leases. President Obama should turn that coal moratorium into a permanent ban -- and extend it to oil and gas.
2. Reinstate America's crude oil export ban
President Obama should immediately halt the export of crude oil under legal authority granted to him by the 2016 Appropriations Act and the National Emergencies Act.
The 40-year-old U.S. ban on crude oil exports was repealed last December. But earlier this year, 350 environmental organizations and other groups filed a legal petition urging the president to declare a national climate emergency and end all U.S. crude exports.
That crucial step would reduce drilling and fracking and could prevent up to 500 million tons of greenhouse emissions -- the pollution equivalent of more than 135 coal-fired power plants, according to a Center for American Progress report.
3. Curb the airline industry's skyrocketing pollution
In July -- after nine years of delay -- the EPA officially acknowledged in an "endangerment finding" that planet-warming pollution from airplanes disrupts the climate. But the agency failed to advance rules to actually reduce aircraft emissions.
That's disturbing given how quickly global aviation emissions are increasing. Airplanes could generate 43 billion tons of planet-warming pollution through 2050, consuming more than 4 percent of the world's entire remaining carbon budget, according to a recent analysis by my organization.
That's why we need ambitious action under the Clean Air Act. The Obama administration still has time to get the ball rolling on strong federal rules that actually reduce this high-flying threat to our climate.
4. Fight false solutions like burning trees for energy
There's nothing clean about cutting down U.S. forests and burning them for energy. So-called "biomass" power plants actually emit about 50 percent more carbon dioxide at the smokestack than coal.
And while logged forests might grow back eventually, re-sequestering some of the carbon, this takes decades to centuries while biomass plants produce emissions that damage the climate today.
Yet there's a disturbing effort in the U.S. Senate to ignore that stark truth. The "biomass carbon neutrality" amendment to the Senate energy bill would dictate that all government agencies automatically consider the use of biomass to be "carbon neutral."
The president can use his power and influence to shut down this anti-science, anti-climate measure.
5. Back stronger international climate action
President Obama hailed recent news that enough countries have ratified the Paris climate agreement for the treaty to enter into force. But there's much more work to do at the international level -- and the president still has time to make a difference at November's United Nation's climate meeting in Morocco.
The Paris agreement alone simply does not provide the strong, just and binding commitments we need to protect the planet's most climate-vulnerable people and our very web of life from climate chaos. Based on our emissions history, the U.S. pollution-cutting pledge was only about 20 percent of what was required based on fairness and science.
When the president's negotiators go to Morocco, they must commit to a worldwide transition to renewable energy and an end to fossil fuel production and use no later than 2050.
And they should make good on our country's promise to contribute money and technical resources for developing countries that are already dealing with massive loss and damage from climate disruption.
If President Obama takes these five steps in his last 100 days in office, he will be remembered as a climate leader.