The science is clear:  Human activity, particularly the burning of fossil fuels – oil, coal and gas – is heating up the planet in ways that have never been seen in recorded history.  According to the third U.S. National Climate Assessment, “Global climate is changing and this is apparent across the United States in a wide range of observations.  The global warming of the past 50 years is primarily due to human activities, predominantly the burning of fossil fuels.”

As the planet heats up, more of it will become uninhabitable.  The majority of the adverse effects of climate change are, and will continue to be, experienced by poor and low-income people around the world.

A report on the global human impact of climate change published by the Global Humanitarian Forum in 2009, projected more than 300,000 deaths and about $125 billion in economic losses each year, and indicated that most climate change-induced mortality is due to worsening floods, droughts, and violence in developing countries.

These are the people who have contributed the least to global warming.

In our affluent nation, the impacts are real, but in the short run are less devastating.  Yet even in the United States, the signs are unmistakable.  Infrastructure is being damaged by sea level rise, heavy downpours, and extreme heat.  These damages are projected to increase with continued climate change.

The rising average temperatures were documented in a report released last week.  The report examined the average summer temperature trend in U.S. cities from the years 1970 through 2016. Summers are trending hotter for 92 percent of the cities analyzed, with locations in Texas and the Mountain region of the West experiencing the most warming since 1970.

The report used data released by the National Centers for Environmental Information, a division of the National Oceanic and Atmospheric Administration, a federal government agency.  The report found average temperature increases for the city of Buffalo, 1.7 degrees, for New York City 0.6 degrees and for the city of Albany a whopping 3.3 degrees.

This is a reminder that even as increasing greenhouse gases raise global temperatures, warming will not be uniform across all areas. Nonetheless, hotter summers raise the risk of heat-related illnesses, such as dehydration, heat exhaustion, and heat stroke.

Yet one year ago, President Donald Trump pledged to withdraw the United States from the world’s effort to curb global warming, the Paris climate agreement.  President Trump described the pact, signed by each and every other nation on Earth, as “an agreement that disadvantages the United States to the exclusive benefit of other countries.”

Despite the compelling scientific evidence that climate change is primarily the result of human activity, and the terrible toll it is taking on humans, other species, and the environment, what led the President Trump to withdraw from Paris?

One can start with willful ignorance; the scientific evidence is overwhelming and the President has chosen to ignore it, likely for political reasons.  Perhaps it was the funding by the fossil fuel industry targeted at influencing the President’s campaign, the transition into the presidency, and the beginning of his administration.

As a practical measure, there is no way for the U.S. — or any other country who signed it — to withdraw from Paris until four years after it went into effect.  Thus, the process of withdrawal can only begin the day after the 2020 U.S. presidential elections.

But there is no doubt that in the meantime, the U.S. federal government will not act to comply with the Paris Agreement.  Thus at best, little will be done by the U.S. during the next few years, at worst the Administration will accelerate the damage caused by the burning of fossil fuels.

Action will need to come at the local and state levels, with decisions by states, cities and institutions to go to net zero emissions.  Of course those pledges must be matched with realistic plans and durable resource-allocation decisions.

And the public must support those efforts and do all it can to make the Trump Administration and its allies pay a political price for their reckless decisions to exacerbate the damage to the world’s climate; decisions that will cost people across the globe their lives, will increase misery for millions, and may harm the fabric of life on earth.

Climate change is an existential threat to life on Earth.  But the challenges aren’t insurmountable—we know how to get to net-zero greenhouse gas emissions.  The rest of the world is moving forward.  The U.S. is indispensable to those efforts.  But for now, the leadership will have to come from the grassroots, local and state government levels.