Dubai, Dec 1 : US President Joe Biden and his Chinese counterpart Xi Jinping were conspicuous by their absence at the Conference of Parties (COP) 28 climate summit here while UAE committed a whopping $38 billion for climate change solutions and unveiled a plan for achieving net zero emissions by 2050. World leaders have gathered here for the COP28 climate change summit including Indian Prime Minister Narendra Modi. But the absence of Biden and Xi is an obstacle to meaningful action on climate change, media reports said pointing out that the US was the biggest carbon emitter followed by China and India. King Charles III and Pope Francis are attending alongside the delegates. The summit's objective is to extract commitments from all nations that the core goal will be to reinforce their resolve in meeting the Paris 2015 UN Framework Convention on Climate Change to limit global warming to 1.5 Celsius a year above pre-industrial levels. Biden had said he would be deputing Vice President Kamala Harris to attend the summit on behalf of the US as White House said he was heavily engaged with the wars in Ukraine, and Gaza war between Israel, and the hostage negotiations. The White House had announced that Biden would not be attending the opening of the summit, and following criticism of the decision announced a last-minute schedule change Wednesday, sending Vice President Kamala Harris in Biden's place. Previously, the most senior US official scheduled to attend had been US climate envoy John Kerry. Biden has attended both of the previous UN climate summits but is facing criticism for his green policies from Republicans, while also facing pressure from younger Democratic voters to take more action to tackle the climate crisis. Instead of Xi, China is being represented at the summit by China's climate envoy Xie Zhenhua. Biden and Xi pass on the chance to inject momentum into talks. The US and China are the world's biggest economies, together accounting for around 38 per cent of the world's greenhouse emissions. The top 20 nations contributing to 8 per cent of carbon emissions are the US, China, India and the European nations. Tom Evans, a policy advisor at think tank E3G, told Business Insider that the decision by the world's most powerful leaders to skip the event was particularly disappointing given they'd recently found common ground on the climate crisis amid escalating tensions on a range of other issues. A stumbling block in the talks at COP28 is the reluctance of some countries in the developing world to agree to tough cuts in emissions that they say would hamper their economic development. /IANS