Catastrophic impacts of climate change are "inevitable", new IPCC report warns

The effects of climate change are “widespread, rapid and intensifying”, according to the latest Intergovernmental Panel on Climate Change (IPCC) report.

Its release comes less than three months before a key climate summit in Glasgow known as COP26.

The report by leading climate scientists published on Monday provides evidence that “unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5 degrees or even 2 degrees will be beyond reach”. In the Paris Climate Agreement, commitments were made to limit global warming to well below 2 degrees, but world leaders never implemented the necessary changes.

The first instalment of the IPCC's sixth assessment report was approved by 195 member governments last Friday. Hundreds of experts who contributed to this report have confirmed it is "unequivocal that human influence has warmed the atmosphere, ocean and land".

It should be emphasised that a small number of major corporations, fossil fuel companies and governmental decisions are responsible for the vast majority of planetary damage, and the impact has disproportionally affected those outside of the Western world up until recent years.

The landmark study also warned of increasingly extreme heatwaves, droughts, extreme rain and flooding (due to rising sea levels), as well as the key temperature limit being broken in just over a decade.

The report "is a code red for humanity", UN Secretary General Antonio Guterres said - though if massive changes were implemented at a quick enough pace, some damage could be halted. There is hope that deep cuts in emissions of greenhouse gases by world leaders could stabilise rising temperatures.

“The alarm bells are deafening, and the evidence is irrefutable: greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk," the UN chief added.

“Global heating is affecting every region on Earth, with many of the changes becoming irreversible. If we combine forces now, we can avert climate catastrophe. But, as today's report makes clear, there is no time for delay and no room for excuses. I count on government leaders and all stakeholders to ensure COP26 is a success."

The report contains the starkest warnings yet about the state of the planet.

Each of the last four decades has been warmer than any decade that preceded it since 1850, with the earth now 1.1C hotter than pre-industrial times. The IPCC uses years 1850-1900 as an approximation for pre-industrial conditions due to the available data to estimate global surface temperature.

Experts are virtually certain that human-caused CO2 emissions are the main driver of acidification of the open ocean, meaning that human influence is presumably the driver of increases in sea levels.

There is more CO2 in the atmosphere than any time in at least 2 million years. Methane and nitrous oxide, which are also greenhouse gases, are at higher concentrations than at any time in at least 800,000 years.

"Some recent hot extremes observed over the past decade would have been extremely unlikely to occur without human influence on the climate system," the report states. Heavy precipitation events, such as rain and snow, have also increased since the 1950s.

In the last few months alone, the world has witnessed hundreds of wildfires across Europe, Siberia, Canada and parts of the US, unprecedented flooding in China, and record high temperatures in North America.

In examining possible climate futures, the IPCC report lays out five possible scenarios to illustrate the climate response to various levels of greenhouse gas emissions, land use and air pollution.

They are called Shared Socio-economic Pathways or SSPs and they start in 2015 – lasting until 2050.

They range from net negative CO2 emissions, whereby more CO2 is taken out than emitted, include emissions staying at current levels, and progress to very high greenhouse gas emissions.

These models also take in socio-economic assumptions, levels of climate change mitigation measures and air pollution controls.

Global warming of 1.5C and 2C will be exceeded this century unless there are drastic reductions in CO2 and other greenhouse gas emissions in the coming decades. Even under the low emissions scenario, the 1.5C warming level is more likely than not to be reached between now and 2040.

With every additional increment of global warming, changes in extreme conditions continue to grow.

"We will see even more intense and more frequent heatwaves," said Dr Friederike Otto, from the University of Oxford, UK, and one of the IPCC report's authors."And we will also see an increase in heavy rainfall events on a global scale, and also increases in some types of droughts in some regions of the world."

Prof Carolina Vera, vice-chair of the working group that produced the document, said: "The report clearly shows that we are already living the consequences of climate change everywhere. But we will experience further and concurrent changes that increase with every additional beat of warming."

Some of the changes already brought about by human activity are irreversible for centuries to millennia, especially changes in the ocean temperature, ice sheets and global sea level. For one, the oceans will continue to warm up for hundreds to thousands of years. Glaciers will continue to melt for decades or centuries and the mean sea level will continue to rise for the rest of the 21st century.

"The consequences will continue to get worse for every bit of warming," said Prof Hawkins of Reading University, UK. "And for many of these consequences, there's no going back."

The report is intended as a reality check, according to IPCC Working Group 1 Co-chair Valérie Masson-Delmotte, who adds that "it's been clear for decades that the Earth's climate is changing and the role of human influence on the climate system is undisputed".

One optimistic point was made by co-chair Panmao Zhai who stated that human actions still have the potential to determine the future course of climate.

"Stabilising the climate will require strong, rapid, and sustained reductions in greenhouse gas emissions, and reaching net zero CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have benefits both for health and the climate."

Ireland's significant agriculture sector should be noted for its methane levels, as well as the growth of energy-draining data centres in the country.

Net zero emissions is an absolute requirement for stabilising CO2 induced global surface temperature increase, as well as reducing methane levels.

Read the IPCC's sobering 2021 report in full below:

ClimateChange 2021: the Physical Science Basis - provides the most updated physical understanding of the climate system and #climatechange, combining the latest advances in climate science, and multiple lines of evidence.

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— IPCC (@IPCC_CH) August 9, 2021