Top 3 spot in roll call of Earth's hottest years awaits despite virus measures

Despite the pandemic-induced lockdowns, climate change continued its relentless march this year, with 2020 on track to be one of the three warmest years on record.

Atmospheric concentrations of greenhouse gases have kept rising, according to the State of the Global Climate 2020 report released by the UN's World Meteorological Organization on Wednesday.

As the world prepares to mark the fifth anniversary of the Paris Climate Agreement on Dec 12, the report makes for grim reading.

"The average global temperature in 2020 is set to be about 1.2 C above the preindustrial (1850-1900) level," WMO Secretary-General Petteri Taalas said in a statement.

"Although we welcome all the recent commitments by governments to reduce greenhouse gas emissions, we are currently not on track and more efforts are needed."

The report said 2011-20 is expected to be the warmest decade on record, with the warmest six years all being since 2015.

This year is very likely to be one of the three warmest years on record globally. The WMO's data sets place 2020 as the second warmest for the year to date, following 2016 and ahead of 2019, according to a news release from the UN agency.

Ocean heat is at record levels and more than 80 percent of the global ocean experienced a marine heat wave at some time in 2020.

The WMO said the world's oceans have recorded increasing acidity due to carbon dioxide absorption creating widespread repercussions for marine ecosystems.

The report, which is based on contributions of dozens of international organizations and experts, shows how high-impact events including extreme heat, wildfires and floods, as well as the record-breaking Atlantic hurricane season, affected millions of people. These events have compounded the threats to human health and security and economic stability posed by the COVID-19 pandemic.

Commenting on the report, Neville Nicholls, emeritus professor from the School of Geography and Environmental Science at Australia's Monash University, said the six warmest years on record－including 2020－h(huán)ave all occurred in the past six years.

Global warming

"This is a testament to the acceleration of global warming," Nicholls said.

"We took about a century for our greenhouse gases to warm the globe by 1 C; we are on track to add another 1 C in just the next 30 years. But there is some hope: China, Japan and South Korea have pledged to be net-zero greenhouse gas emitters by the middle of the century."

If other nations, including Australia, step up emissions reduction efforts and the United States decides to re-join the Paris climate accord, "we may yet avoid the worst consequences of global warming", Nicholls said.

John Church, a professor at the Climate Change Research Centre of the University of New South Wales, said ocean heat content and sea level are two of the most important indicators of climate change.

"Ongoing records of these are updated in this most recent report from the WMO. About 90 percent of the heat accumulating within the climate system from anthropogenic climate change is stored in the ocean," he said.

"This latest update from WMO clearly shows the oceans are continuing to warm, and at an accelerating rate, contributing to sea-level rise. This means climate change has significant momentum, committing us to further change over the coming decades."

Church noted that the rate of sea-level rise is also accelerating, and that the largest contributions are from ocean thermal expansion and the loss of mass from glaciers.

The largest acceleration in the rate of sea-level rise is due to increasing contributions from the ice sheets of Greenland (both surface mass loss and increased glacier outflow) and Antarctica (increased glacier outflow, particularly in West Antarctica), according to the professor.

"These accelerating contributions from the ice sheets are particularly concerning because our ongoing greenhouse gas emissions over the coming decades may commit the world to many meters of sea-level rise over the coming centuries," Church said.

"Slowing and then stopping these rates of change requires urgent, significant and sustained mitigation of our greenhouse gas emissions."