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Climate report: Scale of changes ‘unprecedented’ - but not too late to slow warming

A UN report on climate change has found “deep reductions” in emissions are crucial to limit global warming.

Image: Shutterstock/nicostock

THE CONCENTRATION OF carbon dioxide in the atmosphere was higher in 2019 than any other time in at least two million years, according to a landmark climate report.

Three months ahead of COP26, where world leaders will meet in Glasgow to negotiate climate commitments, a United Nations panel has released a significant report on the current state of the climate.

Authored by climate scientists from around the world, it is the sixth assessment report on the physical science of climate change from the Intergovernmental Panel on Climate Change (IPCC).

The report emphasises that the scale of recent changes to the climate system are “unprecedented” over hundreds and thousands of years and that human influence is the primary driver of global warming.

In 2019, atmospheric carbon dioxide concentrations were higher than at any other time in at least two million years and concentrations of methane and nitrous oxide at their highest for in at least the past 800,000 years.

Now, “deep reductions” in carbon dioxide and greenhouse gas (GHG) emissions are crucial to prevent the planet from warming by more than 1.5 or 2 degrees Celsius.

With a reduction in emissions, it would take at least twenty to thirty years to stablise global temperatures, but benefits for air quality would come more quickly, the report said.

Valérie Masson-Delmotte, co-chair of the IPCC working group behind the report, said that it is a “reality check”.

“We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare,” Masson-Delmotte said.

What’s happening with climate change?

  • The concentration of Co2 in the atmosphere was higher in 2019 than at any other time in two million years
  • Global surface temperatures have increased faster since 1970 than during any other 50-year period in the last two thousand years
  • The annual average Arctic sea ice area was at its lowest in the last decade since at least 1850
  • Global mean sea level has risen faster since 1900 than during any other century in the last 3000 years.

“It is unequivocal that human influence has warmed the atmosphere, ocean and land,” the summary of the report for policymakers states.

“Human influence is very likely the main driver of the global retreat of glaciers since the 1990s and the decrease in Arctic sea ice area between 1979–1988 and 2010–2019,” it says.

“Human influence has warmed the climate at a rate that is unprecedented in at least the last 2000 years.”

Natural drivers in warming are factors such as solar and volcanic activity, but human activities are having a much higher impact, the report found.

“Human-induced climate change is already affecting many weather and climate extremes in every region across the globe,” it says.

These extremes include heatwaves, heavy precipitations, droughts, and tropical cyclones.

In the last forty years, each decade has been successively warmer than any decade that came before it since 1850.

The report sets out five potential futures for the climate that depend on our level of emissions over the coming years – whether they’re very high, high, medium, low or very low.

  • High and very high: GHG and CO2 emissions that double by 2100 and 2050
  • Intermediate (medium): GHG emissions and CO2 emissions remaining at current level until middle of the century
  • Very low and low: GHG emissions and CO2 emissions declining to net zero around or after 2050 followed by net negative CO2 emissions

Under all of the scenarios, global surface temperature will continue to increase until at least the middle of the century, scientists expect.

Even with very low greenhouse gas emissions, global surface temperatures are very likely to be 1 to 1.8 degrees Celsius higher at the end of this century compared to between 1850 and 1900.

IPCC scenarios Projected increase in temperature warming in five scenarios: very low, low, medium, high and very high greenhouse gas emissions Source: IPCC

However, if global net negative carbon emissions are achieved and sustained, the increase in surface temperatures would be gradually reversed.

Reductions in ethane emissions would also limit the warming effect and improve air quality.

Human efforts to remove carbon dioxide emissions that lead to global net negative emissions would “lower the atmospheric CO2 concentration and reverse surface ocean acidification”.

Europe

The report does not make predictions on a country-by-country basis, but looks at climate changes on a regional basis – and for Europe, that means an increase in hot extremes.

The frequency and intensity of hot weather extremes in Europe have risen in recent decades and are expected to continue increasing regardless of the greenhouse gas emissions scenario.

Meanwhile the frequency of cold spells and frost days will decrease while the relative seal level will rise in all European areas except the Baltic Sea.

Extreme sea level events are expected to become more frequent and intense, leading to coastal flooding, and shorelines on sandy costs will retreat.

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In Western and Central Europe, which includes Ireland, climate scientists have observed an increase in hot extremes, in heavy precipitation, and in agricultural and ecological droughts since the 1950s.

If warming rises by two degrees Celsius or above, there are projected increases in pluvial flooding, river flooding, and droughts.

Speaking on RTÉ Radio One this morning, Minister for Environment Eamon Ryan said that the report shows that “doing nothing is not an option”.

Ryan said that the “science is unequivocal that if we don’t make these changes”, the “consequences of not bringing our emissions down” would be drastic.

“We need to start now and we are prepared.”

He said the first important move would be the elimination of fossil fuels.

About the author:

Lauren Boland

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