Key findings:

Significant impacts of climate change are projected already for a warming of 1.5°C above pre-industrial levels for all analysed climate changes and impacts, including temperature extremes, extreme precipitation and dry spells, water availability, crop yield reduction risks for major staple crops, coral reef bleaching and sea-level rise. The results add to a growing body of evidence showing that climate risks occur at lower levels than previously thought.
Projected climate impacts will rise substantially between 1.5°C and 2°C with particularly high increases in heat extremes, the risk of tropical crop yield reductions, coral reef bleaching and subtropical water scarcity.
Tropical and dry subtropical regions emerge as hot spots in which impacts increase most strongly between 1.5°C and 2°C. In combination with limited adaptive capacity and high exposure of most countries in these regions, this point towards a substantial increase in climate change risks.
The results support the analysis of the IPCC AR5 which assessed risks for 3 out of 5 Reasons for Concern to be at least moderate-to-high under a 2°C warming. These three include risks for unique and threatened systems such as coral reefs, risks by extreme events and unequal distribution of risks across geographical regions.

Main results

The 0.5°C warming difference is critical for vulnerable regions

Our assessment implies that differences in climate impacts between 1.5°C and 2°C are most significant and pronounced for regions with limited adaptive capacity and high exposure.

Under a 2°C warming, coastal tropical regions and islands face the combined effects of a complete loss of tropical coral reefs, which provide coastal protection and are a main source of ecosystem services and livelihoods, on-going sea-level rise faster than today and increased threats from coastal flooding and inundation. Limiting warming to below 1.5°C could reduces this risk, as some coral reefs may remain and the rates and levels of sea-level rise are lowered substantially.

Tropical regions emerge as hot-spots for warming trends and agricultural risks. While extreme temperatures at 1.5°C still remain largely within the upper end of currently experienced climate variations, heat extremes that to date would be highly unusual will become the new normal in tropical regions at 2°C.

Risks of substantial regional crop yield reductions are projected. For wheat and maize, projected median yield reductions of local crop yields over the tropical regions double between 1.5°C and 2°C. If highly uncertain effects of CO2-fertilization on future crop yields are excluded, median reductions of 10% are projected for all crop types already under a 1.5°C warming.

Yield reduction and increasing water scarcity increase significantly between 1.5°C and 2.0°C of warming in subtropical dry regions and especially the Mediterranean. Population growth and urbanization in these regions will greatly increase these regions vulnerability to such climate impacts. In conjunction with other development challenges, the impacts of climate change represent a key risk for regional food security.

The Mediterranean region, including North Africa and the Levant, emerges as a hot-spot for severe reductions in water availability and dry spell increases as warming moves from 1.5°C to 2°C: the already water scarce regions faces reductions in water availability of up to 16% under 1.5°C. This risk doubles to almost 30% of potential reduction at 2.0°C of warming.

Read the study

Publications

Humid heat exceeds human tolerance limits and causes mass mortality

With critical physiological limits to human heat tolerance drawing ever closer, this Comment highlights the urgent need to limit further climate warming and emphasises the adaptation challenge ahead.

Spatially resolved emulated annual temperature projections for overshoot pathways

This study presents a new dataset of annual temperature projections for different overshoot pathways (when the 1.5 °C of global warming limit is exceeded). The data offers a unique opportunity to study local and regional climate change impacts of a range of overshoot scenarios, including when temperature thresholds might be exceeded, and by how much.

Geological Net Zero and the need for disaggregated accounting for carbon sinks

This study in Nature show that definitions of net zero now in widespread use will not actually stop global warming. The paper demonstrates that relying on natural carbon sinks, such as in forests or oceans, to 'offset' ongoing fossil fuel emissions will lead to continued warming.

The role of northern forests in limiting warming to 1.5°C

Northern forests are critical in the race to net zero CO₂ by mid-century. Protecting and restoring these forests, alongside steep and rapid reductions in fossil fuel emissions, is essential both to mitigating emissions and to supporting forest ecosystem services and biodiversity.

Rapid urbanisation and climate change key drivers of dramatic flood impacts in Nepal

New study finds the devastating floods in Nepal late September were exacerbated by rapid urbanisation and climate change. The analysis found the relentless rain, which fell on saturated ground in the late monsoon, was made at least 10% heavier and 70% more likely by climate change.

LNG shipbuilding industry heading to huge oversupply

The LNG shipbuilding industry appears to be doubling down on building new carriers, ignoring the global shift to a low carbon economy and putting itself into an even worse oversupply situation than a year ago, we find in our updated report.

Seasonal forecast of two-metre temperature and precipitation in Tanzania: A hybrid cluster and point-by-point machine learning approach

Seasonal forecasting of atmospheric parameters is important in various fields including agriculture. This study tests how machine learning can complement dynamic models using Tanzanian seasonal forecasts and finds this process uses far less computational power.

Overconfidence in climate overshoot

Even if it is possible to reverse the rise of global temperatures after a temporary overshoot of 1.5°C, some climate damages triggered at peak warming, including rising sea levels, will be irreversible, according to a new study published today in Nature.

Fracking the Kimberley: the Canning Basin development plans

We've calculated the climate implications of fracking the Canning basin, part of the remote and pristine Kimberley region in Western Australia. Four companies have their eyes on this region, home to the endangered bilby.

Solar geoengineering: a note to inform discussions on physical climate impacts, risks and governance issues

With international efforts on climate action still not on track to limit warming to 1.5°C, technological fixes that aim to intentionally alter the Earth’s climate, such as solar geoengineering, might seem like appealing options for tackling global warming. But they come with questions in terms of feasibility, impacts and risks, governance and geopolitics, and who may or may not benefit.

How can event attribution science underpin financial decisions on Loss and Damage?

With climate extremes hitting nations across the globe, disproportionately burdening vulnerable developing countries, funding for loss and damage is an acute need. Attribution science can provide useful information for decision makers.

Australia's global fossil fuel carbon footprint

This report unpacks the global carbon footprint from Australia's exported fossil fuels, especially coal and gas; exports that are set to continue at the same level through to 2035, threatening the 1.5˚C warming limit.
Australia has a global carbon footprint that far exceeds its economic size and population - and is responsible for around 4.5% of global fossil carbon dioxide emissions, with 80% of those emissions coming from its fossil fuel exports.

About us

Decarbonisation targets and 1.5℃ pathways

Comment

Briefing note on the assessment “Differential climate impacts for policy-relevant limits to global warming: the case of 1.5°C and 2°C”