GLASGOW - The fingerprints of climate change have been detected in two extreme weather events this year, the World Meteorological Organisation (WMO) said on Sunday (Oct 31).
The heatwave that fried north-west America in June and July would have been "virtually impossible without climate change", said the WMO in its State of Climate 2021 report issued at the start of the United Nations (UN) climate conference COP26.
Similarly, the floods that inundated western Europe in July and killed almost 200 people, along with leaving many more unaccounted for, were made more likely by climate change, said the UN agency.
WMO Secretary-General Petteri Taalas said extreme events are the new norm.
"There is mounting scientific evidence that some of these bear the footprint of human-induced climate change," he added.
Attribution studies is an emerging science that aims to detect the "fingerprint" of climate change on historical extreme weather events.
Professor Taalas said that at the current rate of increase in greenhouse gas concentrations, temperatures by the end of this century would increase beyond targets set out under the Paris Agreement.
Under the agreement, nations have committed to try and take action to limit warming to under 2 deg C - preferably 1.5 deg C - above pre-industrial levels.
But the world has already warmed to about 1.1 deg C above pre-industrial levels. Climate scientists have warned that climate impacts worsen with every deg C of warming, with the UN's Intergovernmental Panel on Climate Change sounding the alarm bells for humanity in a report released in August.
The WMO said in its latest report that the past seven years, including 2021, are on track to be the seven warmest on record.
The assessment was based on data for the first nine months of 2021.
But due to the influence of a La Nina weather event in the early part of the year, 2021 looks set to be "only" the fifth to seventh warmest year on record.
La Nina events are associated with temporary and widespread cooling of the tropical Pacific Ocean - the planet's largest ocean basin. The last significant La Nina event was in 2011.
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Yet, the WMO warned that the temporary cooling due to the influence of La Nina does not negate or reverse the long-term trend of rising temperatures.
"COP26 is a make-or-break opportunity to put us back on track," Prof Taalas added.
In 2015, almost 200 nations adopted the Paris Agreement, which set out goals for limiting global warming but not how they could be achieved.
After three years of negotiations, nations agreed in 2018 to adopt the Paris Rulebook - a guide on how the agreement can be implemented - at COP24 in Poland. The COP26 meeting aims to finalise the details of this implementation.
The WMO report, which combines input from multiple UN agencies, national meteorological and hydrological services and scientific experts, is one of the flagship scientific reports to add urgency to negotiations during the conference.
Other than extreme weather events and temperatures, the report also provides a snapshot of climate indicators such as greenhouse gas concentrations, sea level changes, ocean warming and ocean acidification, glacier retreat and ice melt.
All of these impacts have cascading consequences on human health and livelihoods.
In terms of ocean acidification, the report found that open ocean surface pH - a measure of acidity - has declined globally over the last 40 years and is now the lowest it has been for at least 26,000 years. The lower the pH, the more acidic the object being measured is.
The ocean absorbs around 23 per cent of the annual emissions of carbon dioxide (CO2) generated by humans when they burn fossil fuels and clear forests.
When CO2 dissolves into the ocean, it results in waters becoming more acidic - this has implications for marine life such as hard corals, as more acidic waters make it more difficult for them to form their shells and skeletons.
As the pH of the ocean decreases, its capacity to absorb CO2 from the atmosphere also declines, the WMO added.
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United Nations Secretary-General Antonio Guterres said the report presents the "latest scientific evidence to show how our planet is changing before our eyes".
"From the ocean depths to mountain tops, from melting glaciers to relentless extreme weather events, ecosystems and communities around the globe are being devastated," he said.
"COP26 must be a turning point for people and for the planet."
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