The ACT government has become the first jurisdiction in Australia to join the United Nations-backed Powering Past Coal Alliance aimed at rapidly phasing out the fossil fuel considered a major contributor to climate change.

The move, announced at the Global Climate Action Summit in San Francisco overnight, came as almost 400 investors with $US32 trillion ($45 trillion) unveiled accelerated efforts to meet the Paris Climate Agreement goals to keep global temperatures from rising less than 2 degrees above pre-industrial levels.

Thai protesters gather near the government house to protest the construction of a coal-fired power plant in Bangkok earlier this year. Credit:AP

Shane Rattenbury, the ACT's Climate Change Minister, said the territory would join other alliance members such as France and Mexico, that had agreed to reduce coal's role in electricity generation. It also opposed construction of any plants that don't capture and store carbon dioxide produced.

Mr Rattenbury said his government had joined to cement its leadership, which includes achieving 100 per cent renewable electricity and reaching net-zero emissions by 2045. "[That's] two of the most ambitious climate targets in the world," he said.