Rapid reductions in GHG emissions needed to limit global warming to 1.5 ° C: IPCC

Limiting global warming to nearly 1.5 ° C or even 2 ° C will be impossible unless there are immediate, rapid and large-scale reductions in greenhouse gas (GHG) emissions, a warned the Intergovernmental Panel on Climate Change (IPCC).

In its report Climate Change 2021: The Physical Science Basis, the IPCC said the Earth would warm by 1.5 ° C in all scenarios. Even on the most ambitious emissions trajectory, it will reach 1.5 ° C in the 2030s, exceed 1.6 ° C, before the temperature drops back to 1.4 ° C by the end of the century.

Limiting climate change further would require substantial and sustained reductions in GHG emissions. Without net zero CO2 emissions and sufficient net negative CO2 emissions to offset any further warming, the climate system will continue to warm.

Earlier this year, the United Nations Environment Program released a report that said nations must step up efforts to adapt to the changing climate scenario in order to avoid dire consequences in the future. UNEP’s 2020 Adaptation Gap Report said about 72% of countries have adopted at least one adaptation plan at the national level and most developing countries have one in the works.

According to the report, scientists are observing drastic changes in Earth’s climate in every region and across the climate system. Many of the observed changes, such as rising sea levels and melting polar ice caps, are abnormal and irreversible for the foreseeable future.

The report, compiled by 234 experts from 66 countries over 4,000 pages, describes the processes of human-induced climate change, rising temperatures and projections for the future.

Strong and sustained reductions in CO2 and other greenhouse gas (GHG) emissions would limit climate change, the report said. While the benefits to air quality would occur quickly, it could take at least three decades for global temperatures to stabilize.

“This report reflects extraordinary efforts under exceptional circumstances,” said Hoesung Lee, Chairman of the IPCC. “The innovations in this report and the advancements in climate science it reflects provide invaluable input to climate negotiations and decision-making. “

Rapid rise in temperature

Human activities have been responsible for about 1.1 ° C of warming since the end of the 19e century. Global temperature is expected to rise by or exceed 1.5 ° C on average over the next two decades. This assessment is based on improved observational datasets to assess historical warming and advances in scientific understanding of the climate system’s response to human-made GHG emissions.

“This report 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, ”said Valerie Masson, Co-Chair of the Working Group. I of the IPCC. Demotte.

The report also notes that the Indian Ocean is warming at a faster rate than the world’s oceans. Half of the sea level rise is due to thermal expansion, one of the reasons for sea level rise in the Indian Ocean region. The report concludes that global mean sea level will continue to rise during the 21st century, even under the lowest emission scenarios.

The report predicts that snow covered areas and snow volumes will decrease in most of the Himalayan Hindu Kush, snow line elevations will increase, and glacier volumes will decrease. This is worrying because the Hindu Kush Himalayan region is a crucial source of water supply for millions of Indians.

Ubiquitous changes observed

Global warming directly determines many characteristics of climate change, but what people experience is often very different from the global average. Earth temperatures are skyrocketing above the global average and doubling in the Arctic.

“Climate change is already affecting all regions of the Earth in multiple ways. The changes we are experiencing will increase with further warming, ”said IPCC Working Group I co-chair Panmao Zhai.

The report predicts that over the next decades, climate change will increase in all regions. An increase of 1.5 ° C will lead to increased heat waves, longer summers and shorter winters. An increase of 2 ° C would have devastating effects such as reaching critical tolerance levels for agriculture and health.

The effects of climate change are considerable and are not limited to an increase in temperature. Its effects vary from region to region, sometimes diametrically. Climate change intensifies the water cycle, resulting in intense rainfall and flooding. In contrast, this is also the reason why many regions experience severe drought.

Changes in monsoon precipitation are expected, with higher latitudes receiving increased precipitation. At the same time, in much of the subtropics, it is expected to decrease. Coastal areas will experience a continuous rise in sea level throughout this century, which will promote frequent and severe coastal flooding in low areas and coastal erosion.

Further warming will amplify the thawing of permafrost and the loss of seasonal snow cover, the melting of glaciers and ice caps, and the loss of arctic sea ice in the summer. The oceans will warm with frequent marine heat waves, ocean acidification and reduced oxygen levels, all linked to human influence. These changes affect both ocean ecosystems and the people who depend on them. They will continue for at least the rest of this century.

“Stabilizing the climate will require strong, rapid and sustained reductions in greenhouse gas emissions and the achievement of zero net CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have both health and climate benefits, ”Zhai said.

Changes in the climate system resulting from past, present and future human activities will continue long into the future, even with sharp reductions in GHG emissions. Some aspects of the climate system, including the terrestrial biosphere, deep ocean, and cryosphere, respond much more slowly than surface temperatures to changes in GHG concentrations. As a result, there are already significant committed changes associated with past GHG emissions. For example, global mean sea level will continue to rise for thousands of years, even if future CO2 emissions are reduced to net zero.

Recently, the 2021 Economic Survey found that India would need around $ 206 billion (around $ 15 trillion) between 2015 and 2030 to tackle climate change.

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