More than 70 world leaders were due to address the one-day virtual gathering aimed at building momentum for much steeper cuts in planet-warming emissions on the fifth anniversary of the 2015 Paris climate accord.
In September China announced it would target net zero carbon emissions by 2060, saying it was raising its ambitions for shifting from fossil fuels to renewable energy.
In his short speech, Netanyahu indicated that Israel has substantially reduced its dependency on coal and by 2025 - "barring an emergency" - would no longer burn coal.
Over 122 countries in the climate pact, including China, have communicated their intention to upgrade their goals but have yet to submit new targets, according to a tracker by managed by the Washington-based World Resources Institute.
Israeli PM Benjamin Netanyahu at a joint press conference at the Ministry of Health in Jerusalem, on December 9, 2020.
In the dying days of Donald Trump's administration, the U.S. government was one notable absentee after abandoning the Paris pact.
"Five years ago today, the world gathered to adopt the Paris Agreement on climate change".
The historic accord seeks to limit global warming to less than 2 degrees Celsius, the value that climate scientists have determined will have disastrous consequences if exceeded.
Achieving this will require a phasing-out of fossil fuels and better protection for the world's carbon-soaking forests, wetlands, and oceans.
Guterres, pointing to recent storm-caused floods in Central America as one example, said it was clear support for adaptation needed to be increased "to allow those countries to build the resilience that is necessary for their communities to resist the already inevitable impacts of climate change". "The United States is the largest economy in the world, it's absolutely essential for our goals to be reached".
"The Climate Ambition Summit lacked real ambition".
American representatives at the virtual meeting included Michigan Gov. Gretchen Whitmer, Gov. Charlie Baker of MA and USA business leaders, such as Apple chief executive Tim Cook.
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But major economies including Australia, Brazil and South Africa are absent. Most have offered no significant improvements on their existing emissions targets lately.
The EU, which emits about a tenth of the world's greenhouse gases, showed up with its hard-fought pledge to slash its emissions by 55 percent by 2030.
China would also increase forest stock volume by 6 million cubic meters from the 2005 level and bring total installed wind and solar power capacity to over 1.2 billion kilowatts by that time, he said.
But Xi also cautioned that "unilateralism will lead us nowhere" - a veiled reference to discussions in the European Union to impose tariffs on goods imported from countries that have less stringent emissions standards than the 27-nation bloc.
The Pope has also committed the Vatican to net zero carbon emissions by 2050.
The 189 countries that are party to the Paris agreement are required to submit their updated targets to the United Nations by the end of the year.
"We will take solid steps to implement the targets just announced and contribute even more to tackling the global climate challenge", Mr Xi said via a video message.
"We call on the worldwide community to do the same", he said, noting that rich countries had been promising more technical and financial help "over many decades".
On Friday, summit co-host Britain announced it would pledge to end direct government support for overseas fossil fuel projects at the summit, aiming to spur similar moves by other countries to accelerate a shift to cleaner energy.
Biden, who was President Barack Obama's vice president when the Obama administration negotiated the deal, has repeatedly pledged to rejoin the Paris climate agreement.
"We are counting on the support of the global community to help implement these plans", he said.