‘7 out of 8 climate red lines have already been crossed’

NEW DELHI: Seven of eight earth system boundaries (ESBs) that are critical for stability of the planet’s health and survival of species have already been crossed, a new research paper by the Earth Commission published in Nature journal flagged on Wednesday, suggesting that the very future of humanity may now be at risk from the climate crisis.

Transgression of ESBs is spatially widespread, with two or more ESBs already transgressed for 52% of the world’s land surface, affecting 86% of the global population, the paper said. India, along with other parts of South Asia, Europe, parts of Africa is a ESB transgression hotspot according to a map provided by researchers with the Himalayan foothills experiencing at least five ESB transgressions, the analysis indicated.

The ESB for climate, for example, was crossed at 1 degree C warming over pre-industrial levels and we are today already at 1.2 degrees C warming, 40 researchers from different parts of the world warned in the paper, underscoring that humans are taking colossal risks with planetary systems.

The Earth Commission developed a set of ESBs for climate, the biosphere, fresh water, nutrients and air pollution at global and sub-global scales for the first time referred to in this research paper titled: “Safe and just Earth system boundaries.”

These features were chosen because they span the major components of the Earth system (atmosphere, hydrosphere, geosphere, biosphere and cryosphere) and their interlinked processes (carbon, water and nutrient cycles) or what they call the “global commons” that according to the paper “underpin the planet’s life-support systems and, thereby, human wellbeing on Earth; they have impacts on policy-relevant timescales; they are threatened by human activities; and they could affect Earth system stability and future development globally.”

The seven ESBs that have been crossed are: climate (two local exposure boundaries – wet bulb temperatures of over 35 °C for at least one day of the year and extent of low-elevation coastal zones), functional integrity, and levels of surface water, groundwater, nitrogen, phosphorus and aerosols.

The eighth, which has not been crossed, is under two heads. In climate, 1.5 degree C warming is still “safe” but not ”just.” “Safe and just” was crossed at 1 degree C. The global annual mean interhemispheric aerosol optical depth (AOD) difference, a proxy for degree of air pollution globally has also not been crossed.

The safe ESBs for global warming is based on minimizing likelihoods of triggering climate tipping elements and maintaining biosphere and cryosphere functions, the Earth Commission said. “We find that global warming beyond 1 degree C above preindustrial levels, which has already been exceeded , carries a moderate likelihood of triggering tipping elements, such as the collapse of the Greenland ice sheet or localized abrupt thawing of the boreal permafrost… above 1.5 degree C or 2 degree C warming, the likelihood of triggering tipping points increases to high or very high,” the paper states while adding that at 1.5 to 2 degree C, biosphere damage and the risk of global carbon sinks becoming carbon sources, potentially triggering further climate feedbacks, increase substantially.

For the biosphere, the team proposes an ESB of 50-60% of global land surface covered by largely intact natural areas to maintain various natural functions but this also has already been breached.

About two thirds of human dominated land area (approx 40% of total land area) has insufficient functional integrity and large areas are showing symptoms of resilience loss according to the paper.

For water bodies and rivers, the researchers recommend an ESB of 20% monthly water flow alteration which leaves 80% of flows unaltered to meet environmental needs. But this too was breached for 34% of land surface.

ESBs have also been transgressed globally for agricultural nitrogen (N) and phosphorus (P) excesses for minimizing eutrophication of surface water and land ecosystems due to runoff, leaching and atmospheric ammonia and nitrogen oxide emissions. The ESB for air pollution has also been breached, particularly for the South Asia region.

The ESB according to the team is 15 μg/m3 of mean PM2.5 (fine, respirable particulate matter) concentrations annually but 85% of the world population is currently exposed to PM2.5 concentrations beyond this , and exposure to ambient PM2.5 is estimated to cause 4.2 million deaths, the paper said. It also flagged that high air pollution levels over the region may be impacting both the Indian and West African monsoon.

The world has already passed the safe and just climate boundary, which is set at 1 degree C above pre industrial temperature levels, as tens of millions of people are already harmed by the current level of climate change, researchers said. “Our results are quite concerning: Within the five analyzed domains, several boundaries, on a global and local scale, are already transgressed. This means that unless a timely transformation occurs, it is most likely that irreversible tipping points and widespread impacts on human well-being will be unavoidable.

Avoiding that scenario is crucial “if we want to secure a safe and just future for current and future generations,” said Prof. Johan Rockström, Earth Commission Co-Chair, lead author and Director of the Potsdam Institute for Climate Impact Research in a statement on Wednesday.

“The Earth system is in danger, as many tipping elements are about to cross their tipping points,” explained Prof. Dahe Qin, Co-Chair of the Earth Commission and Director of the Academic Committee, Chinese Academy of Sciences in a statement.

“Warming has already happened. There has been a lot of discussion around climate tipping points like loss of Amazon forests and loss of permafrost in the Arctic. We now know that the 1.5 degree C goal may not materialise, we may go up to 2 degree C warming. I cannot say if tipping points and safe boundary limits have already been reached because they are not defined very objectively. However, with 1.5 degree C warming tipping points will definitely be breached and cascading impacts on atmosphere will be felt. With every additional increment of global warming, changes in extremes continue to become larger,” said M Rajeevan, climate scientist and former secretary, ministry of earth sciences said.

Overshooting 1.5 degree C warming would lead to irreversible impacts and risks for human and natural systems, all growing with the magnitude and duration of overshoot, Intergovernmental Panel on Climate Change, the key scientific authority on climate crisis warned in March.