The goal of limiting global temperature rises to 1.5 degrees or even two degrees Celsius will soon be out of reach without urgent action to limit greenhouse gas emissions, a comprehensive report prepared by more than 200 scientists from around the world as warned.

Releasing its latest report, the Intergovernmental Panel on Climate Change said that it was ‘unequivocal’ that human influence has warned the atmosphere, ocean and land from around 1750 onward.

Going forward, it says the world will likely reach or exceed a 1.5°C temperature increase by 2040 – much faster than previously thought.

It warns that without immediate and large-scale reductions in greenhouse gas emissions, the goal of restricting temperature rises to 1.5°C or even 2°C will soon be out of reach.

According to the report:

• Atmospheric concentrations of greenhouse gasses have continued to rise since the last report in 2011 and have now reached annual averages of 410 ppm for carbon dioxide (CO2), 1866 ppb for methane (CH4), and 332 ppb for nitrous oxide (N2O) in 2019.
• Each of the last four decades has been successively warmer than any decade that preceded it since 1850.
• Based on best estimate, human induced factors have driven a 1.07 degree increase in global surface temperature throughout the first two decades of 2020 compared with annual average surface temperatures which were observed throughout 1850 to 1900. Even after a slight cooling effect due to factors such as aerosols, this contributed to an overall increase in surface temperatures of 1 degree (0.99 degrees).

Source: Climate Change 2021 The Physical Science Basis Summary for Policymakers, Intergovernmental Panel on Climate Change, 2021

In its report, the IPCC warns of significant climate impacts over coming decades.

For 1.5°C of global warming, these include increasing heat waves, longer warm seasons and shorter cold seasons.

At 2°C of global warming, heat extremes would more often reach critical tolerance thresholds for agriculture and health.

Moreover, the report warns that the effects will extend beyond temperature and encompass changes to wetness, dryness snow and ice, coastal areas and oceans.

These effects include:

• A more intense water cycle with more intense rainfall and associated flooding along with more intense drought in many regions.
• Altered rainfall patterns with more rain in higher latitudes and less precipitation over the subtropics along with changes in monsoon rainfall which will vary by region.
• Continued sea level rise throughout the 21st century, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion.
• Amplified permafrost thawing along with the loss of seasonal snow cover, melting of glaciers and ice sheets and loss of summer Arctic Sea ice.
• Changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels have been clearly linked to human influence.
• Amplified challenges in cities and urban areas such as urban heat (since urban areas are usually warmer than their surroundings), flooding from heavy rain and sea level rise in coastal cities.

The impact of these consequences should not be underestimated.

Extreme temperature events which occurred only once per decade between 1850 and 1900 now occur 2.8 times decade.

Under warming scenarios of 1.5°C and 2°C, these are likely to occur 4.1 times and 5.6 times per decade respectively.

Broadly similar observations can be seen for other climate events such as heavy rainfall and drought (see chart).

By the end of the century, meanwhile, extreme sea level events that previously occurred once in 100 years could happen every year.

Aforementioned change to the oceans, meanwhile, will affect both ocean ecosystems and the people that rely on them.

This will continue throughout at least the rest of this century, the report warns.

IPCC Working Group Co-Chair Panmao Zhai said the importance of addressing climate change should not be underestimated.

“Climate change is already affecting every region on Earth, in multiple ways. The changes we experience will increase with additional warming,” Zhai said.

“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.”

Source: Climate Change 2021 The Physical Science Basis Summary for Policymakers, Intergovernmental Panel on Climate Change, 2021