'Climate Change 2021: The Physical Science Basis' IPCC’s Sixth Assessment Report

The Sixth Assessment Report has been finalised and approved by 234 authors and 195 governments and updates the scientific consensus on extreme weather, human attribution, the carbon budget, feedback cycles, and charts the future state of the climate since the Fifth Assessment Report of 2014. The 3,000-plus-page report said warming is already accelerating sea level rise and worsening extremes such as heatwaves, droughts, floods and storms.

• The Indian Ocean is warming at a higher rate than other oceans, said the latest report by the Intergovernmental Panel on Climate Change (IPCC), with scientists warning that India will witness increased heatwaves and flooding, which will be the irreversible effects of climate change.
• The current overall global warming trends are likely to lead to an increase in annual mean precipitation over India, with more severe rain expected over southern India in the coming decades.
• The authors of the IPCC’s Sixth Assessment Report, “Climate Change 2021: The Physical Science Basis”, said the warming of the ocean would lead to a rise in sea levels, leading to frequent and severe coastal flooding in low-level areas.
• With a 7,517-km coastline, India would face significant threats from the rising seas. Across the port cities of Chennai, Kochi, Kolkata, Mumbai, Surat and Visakhapatnam, 28.6 million people would be exposed to coastal flooding if sea levels rise by 50 cm.
• Monsoon extremes are likely to increase over India and South Asia, while the frequency of short intense rainy days are expected to rise. Models also indicate a lengthening of the monsoon over India by the end of the 21st century, with the South Asian monsoon precipitation projected to increase.
• Stating that human activities are causing climate change, the report said the planet was irrevocably headed towards warming by 1.5 degrees Celsius over pre-industrial times in the next two decades.
• Keeping global warming below 2 degrees Celsius of pre-industrial levels by the turn of century and endeavouring to limit it to 1.5 degrees Celsius was at the heart of the 2015 Paris Agreement.
• Unless extremely deep emission cuts are undertaken by all countries immediately, these goals are unlikely to be met. The report recommended that countries strive to achieve net zero emissions — no additional greenhouse gases are emitted — by 2050.
• In the most ambitious emissions pathway, the projection is that the globe would reach the 1.5 degrees Celsius scenario in the 2030s, overshoot to 1.6 degrees Celsius, with temperatures dropping back down to 1.4 degrees Celsius at the end of the century. India has not yet committed to a net zero timeline.

Tropical cyclones

• Tropical cyclones are getting stronger and wetter, while Arctic Sea ice is dwindling in the summer and permafrost is thawing. All these trends will get worse, the report said.
• India is currently the world’s third largest greenhouse gas emitter, but per capita emissions are much lower.
• The U.S. emitted nearly nine times more greenhouse gases per capita than India in 2018. Based on existing commitments by countries to curb their emission, the world is on track for global temperature warming by at least 2.7°C by 2100, predicts the report, calling it ‘Code red for humanity’.
• The latest scientific assessment will influence discussions on the Conference of Parties meeting in Glasgow later this year where countries are expected to announce plans and steps they have taken to curb emissions. The report release follows a two-week long plenary session held virtually from July 26 to August 6, 2021, in which the report was scrutinized line-by-line for approval by government representatives in dialogue with report authors.

Hot extremes

• Alok Sharma, COP26 President, said in a statement: “The science is clear. The impacts of the climate crisis can be seen around the world and if we don’t act now, we will continue to see the worst effects impact lives, livelihoods and natural habitats. Our message to every country, government, business and part of society is simple. The next decade is decisive, follow the science and embrace your responsibility to keep the goal of 1.5C alive. We can do this together, by coming forward with ambitious 2030 emission reduction targets and long-term strategies with a pathway to net zero.”
• “Developed Countries have usurped far more than their fair share of the global carbon budget. Reaching net zero alone is not enough, as it is the cumulative emissions up to net zero that determine the temperature that is reached. This has been amply borne out in the IPCC report. It vindicates India’s position that historical cumulative emissions are the source of the climate crisis that the World faces today,” Environment Minister Bhupendra Yadav said in a statement.

Glaciers will keep shrinking

• Glaciers in the Hindu Kush Himalayan (HKH) region will keep shrinking and the snow cover will retreat to higher altitudes, the latest IPCC report said on Monday.
• The Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC), approved by 195 member-countries, warned that extreme precipitation is projected to increase in major mountainous regions with potential cascading consequences of floods, landslides and lake outbursts in all scenarios.
• One of the authors of the report, Krishna Achuta Rao, said that in the HKH region, the snow cover had reduced since the early 21st century and glaciers had thinned, retreated and lost mass since the 1970s. However, he said, the Karakoram glaciers (is an exception) had either slightly gained mass or were in an approximately balanced state.
• “Snow-covered areas and snow volumes will decrease during the 21st century, snowline elevations will rise and glacier mass is likely to decline with greater mass loss in higher greenhouse gas emission scenarios. Rising temperatures and precipitation can increase the occurrence of glacial lake outburst floods and landslides over moraine-dammed lakes,” Mr. Rao said.
• According to the report, mountain glaciers will continue to shrink and permafrost to thaw in all regions where they are present.
• Another author of the report, Swapna Panickal, who is a scientist at the Indian Institute of Tropical Meteorology, said human influence was responsible for the retreat of glaciers since the 20th century and that was not only the case in the two poles, but also for mountain glaciers.