2019•09•20     Tokyo

New research published in Science expands on the 2018 Intergovernmental Panel on Climate Change (IPCC) special report, Global Warming of 1.5°C, by examining the benefits, risk levels, and implications for environment, human health, and economies if warming is limited to 1.5°C versus 2.0°C. The publication — The Human Imperative of Stabilizing Global Climate Change at 1.5°C — is co-authored by UNU expert Riyanti Djalante, who is also a lead author of the IPCC’s Special Report and Assessment Report 6.

In 2017, global mean surface temperatures (GMST) reached 1.0°C above the pre-industrial period. Stating how this has “fundamentally transformed our planet and its natural systems”, the publication’s authors point to potent examples of how increases in the frequency and/or duration of terrestrial and marine heatwaves, as well as shifting and intensifying weather patterns, have had impacts on natural and human systems and have disrupted the interdependence of ecosystems, livelihoods, and economies.

But with GMST projected to reach 1.5°C within decades, this imminent threat has focused international attention on the feasibility of efforts to stabilise temperatures, the benefits of successfully doing so, and the risks and implications of reaching 2.0°C.

Through comprehensive review of scientific approaches that quantify risks for natural and human systems at 1.5°C and 2.0°C, the authors present how “accelerating risk” is “likely to drive proportionally and possibly exponentially higher risk levels in the transition from 1.5°C to 2.0°C”. Perhaps most urgent is evidence that our current transition period from 1.0°C to 1.5°C will involve much greater risks than those seen during the increase from 0.5°C to 1.0°C. And as temperatures and risks increase, ecosystems and organisms that might appear to be healthy could reach sudden temperature “tipping points” leading to their collapse.

The authors note that an accelerating amount of peer-reviewed scientific literature since the Paris Agreement and the IPCC Special Report has made it “very clear that there is an even more compelling case for deepening commitment and actions for stabilizing GMST at 1.5°C above pre-industrial levels”.

Key conclusions of the research include:

• “Multiple lines of evidence reveal that a 1.5°C world will entail larger risks to both human and natural systems. The risks of a 2.0°C world are much greater.”
• “Benefits of avoided damage by the year 2200 may greatly exceed energy sector investment costs to 2050.”
• “Immediate and transformative action is required between now and 2030 in order to greatly scale up current nationally stated plans for greenhouse gas reductions.”
• “Strategies for responding to climate change must be scalable to the challenges of climate change being faced today and into the future, while at the same time being feasible and fair.”
• “There is an increasing need for large scale strategies such as the UN Climate Resilient Development Pathways or ‘Green New Deal’ (UN Environment Programme) if society is to avoid potentially catastrophic circumstances over the next few decades and century.”

To read the full publication, visit the Science website.