In 2015, during the lead-up to the Paris conference on climate change, the USA submitted its "Nationally Determined Contribution", committing to reduce emissions 26 to 28 percent by 2025 (based on 2005 levels).
Nutall said that while the United Nations welcomes the initiative from US cities, states, and businesses, the challenge will be quantifying the effect of climate action from diverse and potentially overlapping actors, a process that will likely stretch well beyond this year's climate conference.
The "America's Pledge" initiative includes an analytical effort lead by the Rocky Mountain Institute and the World Resources Institute. "We're already halfway there".
Brown is serving as a special adviser to states and regions at the Germany gathering, while Bloomberg was appointed a special envoy for cities and climate change in 2014 by U.N. Secretary-General Ban Ki-moon.
A coalition of US states, cities, businesses and colleges is committing to reduce greenhouse gas emissions as prescribed under the so-called Paris climate agreement, even after President Trump deemed the pact "unfair" and called for America to withdraw. The initiative announced Wednesday is called "America's Pledge".
"The American government may have pulled out of the Paris Agreement, but American society remains committed to it - and we will redouble our efforts to achieve its goals", said Bloomberg in a statement.
The accord was negotiated by 195 countries under the United Nations Framework Convention on Climate Change and adopted by consensus in 2015, and is set to take effect in 2020.
The Trump Administration may have walked away from the Paris Accord, but that policy shift is not stopping other political leaders and the private sector from moving forward on climate action. Bloomberg, meanwhile, met with France's President Emmanuel Macron and Paris Mayor Anne Hidalgo within 24 hours of the White House's announcement of the about-face on the Paris Agreement to assure global leaders that many parties in the USA were still committed to tackling climate change. "The effort to aggregate and quantify the actions of subnational authorities and non-Party stakeholders in the United States via "America's Pledge" is welcome".
"Something could happen with respect to the Paris accord, let's see what happens", said Trump, Xinhua reported.
Outside experts with the World Resources Institute and the Rocky Mountain Institute, two USA -based non-profits, have been retained to conduct the study on current and projected emissions of "America's Pledge" affiliates.
"This is demonstrably not an issue that can be addressed by national governments alone", he said. "If it happens, that will be wonderful, and if it doesn't, that'll be OK too", President Trump said.
Presenting the legislative package to state senate lawmakers yesterday, Brown argued there was an urgent need to combat climate change, which he described as a "threat to organised existence", according to US News.