U.N. climate negotiations get underway in Brazil, with leaders urging urgency and cooperation to curb global warming. The Trump administration is not participating.

A group of activists skirmished with security on Tuesday at United Nations climate talks in Brazilian Amazon city Belem, briefly trying to force their way into the main venue before they were pushed back.

Gavin Newsom, a likely Democratic presidential candidate, is the most senior U.S. politician to attend the COP30 summit so far.

There are other thorny issues to tackle for delegates who do attend the negotiations, including a plan to scale up climate finance to $1.3 trillion annually to help communities recover from climate disasters, adapt to the even more extreme changes ahead, and build out more carbon-free sources of energy.

The United States has put more heat-trapping carbon dioxide into the air from the burning of coal, oil and natural gas than any other country. China is the No. 1 carbon polluter now, but because carbon dioxide stays in the air for at least a century, more of it was made in the U.S.

Several Senate Democrats break ranks to join Republicans in a deal to reopen the government. And, world leaders gather in Brazil for a major climate conference, but the U.S. is not expected to attend.

UCSD is sending a delegation of students to COP30 to share scientific research, as well as bring back knowledge to directly impact.