IPCC 1.5 Degree Report

You are very unlikely to have missed the various media reports about the IPCC’s special report on global warming of 1.5 °C, published this week. Some of the comparisons between a 1.5°C world and a 2°C world are fairly shocking, even to someone who had a fair understanding of climate projections. The full summary of the report can be found here – but here are a few headlines which I have extracted from it:

  • Human activities are estimated to have already caused approximately 1.0°C of global warming above pre-industrial levels
  • If we stopped all emissions now, we would probably stay within 1.5°C warming.
  • If we do very little now, we are likely to reach 1.5°C warming by the 2050s at the latest.
  • – Climate-related risks for natural and human systems are higher for global warming of 1.5°C than at present, but lower than at 2°C
  • Climate related risks are larger if global warming exceeds 1.5°C before returning to that level by 2100 than if global warming gradually stabilizes at 1.5°C
  • By 2100, global mean sea level rise is projected to be around 0.1 metre lower with global warming of 1.5°C compared to 2°C. This would mean 10 million fewer people would be affected.
  • At somewhere between 1.5°C and 2°C, major ice sheet instability in Antarctica and/or irreversible loss of the Greenland ice sheet could be triggered, resulting in multi-metre rise in sea level over hundreds to thousands of years.
  • Limiting global warming to 1.5°C compared to 2°C is projected to lower the impacts on terrestrial, freshwater, and coastal ecosystems and to retain more of their services to humans. Of 105,000 species studied, 6% of insects, 8% of plants and 4% of vertebrates are projected to lose over half of their climatically determined geographic range for global warming of 1.5°C, compared with 18% of insects, 16% of plants and 8% of vertebrates for global warming of 2°C
  • With 1.5°C of global warming, one sea ice-free Arctic summer is projected per century. This likelihood is increased to at least one per decade with 2°C global warming.
  • Coral reefs are projected to decline by a further 70–90% at 1.5°C with larger losses (>99%) at 2ºC
  • Depending on future socioeconomic conditions, limiting global warming to 1.5°C, compared to 2°C, may reduce the proportion of the world population exposed to a climate-change induced increase in water stress by up to 50%
  • Estimates of the global emissions outcome of current nationally stated mitigation ambitions as submitted under the Paris Agreement would lead to global greenhouse gas emissions in 2030 of 52–58 GtCO2eq yr-1. These ambitions would not limit global warming to 1.5°C, even if supplemented by very challenging increases in the scale and ambition of emissions reductions after 2030. Avoiding overshoot and reliance on future large-scale deployment of carbon dioxide removal can only be achieved if global CO2 emissions start to decline well before 2030. The lower the emissions in 2030, the lower the challenge in limiting global warming to 1.5°C after 2030 with no or limited overshoot
  • Mitigation options consistent with 1.5°C pathways are associated with multiple synergies and trade-offs across the Sustainable Development Goals, particularly health, clean energy, cities and communities, responsible consumption and production, and oceans.

Carbon Brief: Scientists discuss key findings of the IPCC special report.
Carbon Brief: Q&A on the IPCC special report on climate change.
The Office for Climate Education’s Summary for Teachers.

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