Politicians in the United States have long disagreed on what, if anything, the government should do about climate change. That division has perhaps never been so stark as it is in the current presidential campaign.

Democratic nominee Hillary Clinton calls climate change "an urgent threat and a defining challenge of our time," and her Republican challenger Donald Trump has said it is a "hoax."

In the second conversation from Here & Now's climate change series, Evan Lehmann, deputy editor of ClimateWire, joins Here & Now's Jeremy Hobson to discuss the partisan politics of climate science and the history of cap-and-trade — the failed climate bill that would have set limits on greenhouse gas emissions.

Evan Lehmann, deputy editor of Environment & Energy Publishing's ClimateWire. He tweets @evanlehmann.