86% of global population affected by subglobal climate change

A new study by 40 scientists and researchers from across the globe has quantified that humanity has transgressed several safety boundaries of the five components of earth system and called for urgent transformative action, noting that about 86 per cent of the global population faces risk by the current transgressions.

In the article 'Safe and just Earth system boundaries' published by Nature, the researchers looked into five key domains that span the major components of the Earth system: atmosphere, hydrosphere, geosphere, biosphere and cryosphere. The domains and their interlinked processes -- carbon, water and nutrient cycles -- underpin the planet's life support systems, the study said.

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The researchers identified safe and just earth system boundaries (ESB) for climate, the biosphere, fresh water, nutrients and air pollution at both global and sub global scales.
For instance, the study put the biosphere boundary at up to 60 per cent of the terrestrial earth's surface becoming a natural area allowing ecological functions. "If these boundaries are transgressed, tipping points involving loss of biome-scale functional integrity and associated NCP may be triggered, including increases in species extinction rates," the study said.
Past scientific attempts to define environmental boundaries, such as the planetary boundary framework, have looked at the global conditions needed to maintain a stable planet to safeguard life on earth.

"The new research provides safe and just ESBs for five critical domains that play a key role in life support and Earth stability. It also explores what's needed to minimise significant harm to humans as a result of changes in the Earth system and sets boundaries at scales relevant for assessment and management of the conditions of biophysical systems such as the biosphere and freshwater," said Steven Lede, lead author and Research Scientist, Earth Commission Secretariat, Future Earth, Australian National University and Stockholm Resilience Centre.
While safe boundaries ensure stable conditions, just boundaries seek to minimise human exposure to significant harm.
The study set the climate ESB at 1 degree C, said Joyeeta Gupta, Co-Chair of the Earth Commission, Professor of Environment and Development in the Global South at the University of Amsterdam and Professor of Law and Policy in Water Resources and Environment at IHE Delft Institute for Water Education. "We are not advocating that the world should adopt this ambitious target (1 degree C), but we are exposing the injustice inherent in the current world targets," she said.

It said seven of the eight global-scale safe and just ESBs have already been crossed. "Transgression of ESBs is spatially widespread, with two or more safe and just ESBs transgressing for 52 per cent of the world’s land surface, affecting 86 per cent of the global population. Some communities experience many ESB transgressions, with four or more ESBs transgressing for 28 per cent of global population but only 5 per cent of global land surface. Spatial hotspot transgressions are therefore concentrated in regions of higher population density, raising major intragenerational justice concerns," it said.

Dahe Qin, co-chair of the Earth Commission and Director of the Academic Committee, Chinese Academy of Sciences said the Earth system was in danger. "So far, 17 tipping elements are identified in scientific literature, among them nine are cryosphere-related. The Asia High Mountain Cryosphere (AHMC) is fast changing and close to becoming a new tipping element, which can impact the regional social-economy," he said.
The study recommended that some boundaries be made more stringent to protect present generation, local-level standards and measures to ensure that the transition is just.