Ride-sharing company Lyft has announced an ambitious set of "climate impact goals" which it hopes will help cut CO2 emissions from the U.S. transportation sector by "at least" five million tons per year by 2025.

In a blog post towards the end of last week, co-founders John Zimmer and Logan Green described climate change as "one of the defining issues and greatest global threats of our time."

Lyft's goals include all electric autonomous vehicles on its platform being powered by 100 percent renewable energy, and Lyft's shared platform providing "at least" one billion rides annually "using electric autonomous vehicles", also by the year 2025.

Setting out their aims, the co-founders said they were doing their part "to ensure the United States remains on track to meet the goals of the Paris Accord."

Under that agreement, reached at the end of 2015, world leaders have committed to making sure global warming stays "well below" 2 degrees Celsius and to pursue efforts to limit the temperature rise to 1.5 degrees Celsius.

On June 1, President Donald Trump announced the U.S. would withdraw from the agreement and start talks to re-enter or renegotiate a new accord. "This agreement is less about the climate and more about other countries gaining a financial advantage over the United States," he said at the time.