The US officially pledged to reduce emissions by 50-52% by 2030 compared to 2005 levels, a move that, if successful, would overhaul the world's second largest emitter's entire energy infrastructure, ranging from the cars people drive to how they would heat and power their homes. 

The target is designed to ensure the US takes a leading role on the world stage in tackling climate change, as President Joe Biden vowed to do when he came to office last year. 

"Taking on climate change together is more than just the right thing to do; it's also in everyone's best interests to do it," Biden said.  

"The private sector is already recognizing this.  They know that climate change is more than a threat.  It also presents one of the largest job creation opportunities in history."  

Climate Action Tracker said the updated National Determined Contribution (NDC) represented major progress beyond the previous US targets of 26-28% below 2005 levels by 2025 - but said it was not quite enough to bring its emissions in line with keeping global heating to 1.5C. 

The American Petroleum Institute said the updated NDC only addressed half of the dual challenge of reducing emissions while ensuring energy was reliable and affordable - calling for a transparent price on carbon to incentivise companies to lower emissions. 

"With a transparent price on carbon and innovation, we can make measurable climate progress within this decade without hurting America's middle class, jeopardizing US national security, and undermining economic recovery," API CEO Mike Sommers said. 

"We are focused on working with Congress and the administration on effective government policies, while accelerating industry initiatives and innovation."

The API has previously said it would only support a price on carbon if it meant all other environmental regulation was rescinded. The Biden administration has not voiced its support for a carbon price, and Republicans in congress would likely block any attempt to pass one. 

Japan meanwhile - Australia's biggest coal and LNG customer - announced it would reduce emissions by 46% below 2013 levels by 2030 with a stretch target of 50%, after coming under heavy pressure from the US.  

To do this, Japan would need to phase out its coal-fired power stations and accelerate renewable capacity deployment. Japan's government is expected to release its Strategic Energy Policy later this year which it has indicated it will aim for lower use of coal and gas in the electricity mix. 

China did not update its emission targets, but said it will peak emissions from coal-fired power stations by 2025; Canada said it would reduce emissions by 40% by 2030; Other major energy exporters including Russia and Brazil did not update their targets, while earlier this week the UK said it would cut emissions by 78% by 2030. 

Australia meanwhile did not update its targets, repeating arguments the government has made in recent weeks that technological advancements to solve the issue of how to reduce emissions was more important than targets setting out when those emissions would fall. 

"Our goal is to get there (net-zero) as soon as we possibly can, through technology that enables and transforms our industries, not taxes that eliminate them and the jobs and livelihoods they support and create, especially in our regions," he said. 

"Future generations, my colleagues and excellencies, will thank us not for what we have promised, but what we deliver."

The government recently announced an extra A$500 million on hydrogen and CCS development - with Morrison saying Australia was creating a "hydrogen valley" to help lower emissions. 

Investor Group on Climate Change CEO Emma Herd said the targets acted as market signals to global capital markets and could help Australia unlock billions in investment. 

"Many investors and businesses are moving ahead of national governments in setting their own emissions goals," she said. 

"If Australia was to adopt emissions targets consistent with the goals of the Paris Agreement, and a policy framework to achieve it, then it could create A$131 billion in fresh domestic investment opportunities alone by 2030 and more again in export industries."

More updated targets are expected to be announced at the next round of talks at COP26 in Glasgow in November, however a US official told media it expected Australia to lift its game. 

"Our colleagues in Australia recognise there's going to have to be a shift," the official said. 

"It's insufficient to follow the existing trajectory and hope that they will be on a course to deep decarbonisation and getting to net zero emissions by mid-century."