NEW DELHI: The United Nations Environment Programme has said that global temperature rise due to climate change is expected to exceed the 1.5°C mark, which was conceived earlier. More importantly, it has said that this breach is likely to take place within the next few years, pushing climate risks to increasingly dangerous levels.
In a report titled “Limiting Overshoot”, the UN body said that the most optimistic scenario suggests that temperature rise may peak at 1.8°C above pre-industrial levels, while other scenarios predict even higher peaks.
The UN body said that strong political will, multilateral cooperation, effective policies, inclusive governance and financial support are crucial enabling conditions for effective action, noting that such an approach should be rooted in the principles of equity and justice. It said that countries with a greater responsibility for climate change should act swiftly and with highest ambition.
The report also states that the rising temperatures are leading to a faster rate of acidification in the Indian Ocean, which is shrinking the habitable zone of marine ecosystems by 200 meters. This faster acidification will make it more difficult for certain sea animals, particularly marine calcifiers, like corals, oysters, clams and some types of plankton, to build and maintain their shells or skeletons. Ocean acidification occurs when seawater becomes more acidic due to the ocean absorbing carbon dioxide from the atmosphere.
In addition to the Indian Ocean, the North and Central Pacific Oceans are also experiencing similar declines in marine calcifiers, which have resulted in a reduction in vertical habitable zones. For example, if a species could previously inhabit waters from the ocean surface down to 500 meters, acidification might limit that range to only the upper 300 meters. The Arctic Ocean is becoming acidic much faster—about three to four times—than most other oceans.
The report states that once temperatures exceed 1.5°C, risks and impacts will intensify with every fraction of the jump. Anticipated impacts include more extreme weather, loss of ecosystems and the submersion of Small Island Developing States as well as low-lying coastal cities. The UN body anticipates severe damage to human health, food security, water supplies, nature, cities, infrastructure and economies in years to come.
The report warns of the likelihood of crossing irreversible tipping points, such as the destabilisation of major ice sheets, degradation of the Amazon rainforest and disruption of Atlantic Meridional Overturning Circulation (which is crucial for regulating the climate by moving warm surface water north and cold deep water south). Some impacts may occur abruptly, while others will accumulate over time.
However, the report also states that it is still possible to lower temperatures and achieve the global goals set out in the Paris Agreement. It identifies a pathway of “overshoot, peak and decline” as the best remaining option to minimise the magnitude and duration of temperature overshoot and work toward returning to below 1.5°C as soon as possible.
This pathway, the report noted, would minimise peak temperature rise through immediate and sustained cuts to greenhouse gas emissions, including methane, on the road to net-zero, and bring down temperatures through long-term net-negative emissions, with carefully governed Carbon Dioxide Removal—the process of removing carbon from the air and storing it through afforestation or other means—an essential part of the mix.
It added that, at the same time, following this pathway would involve adaptation actions that reduce vulnerability to the current, expected and unexpected impacts of climate change on societies.