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

The impacts of multiple tropical cyclone events and associated precipitation on household income and expenditures

Climate change-fueled tropical cyclones have already reduced household incomes across the Philippines by 7% on average, according to a new study. This figure rises to more than 20% in some provinces.

What good looks like: G7 climate policy 2024 update

This brief outlines seven key policy recommendations for this June’s G7 summit that, if adopted, would demonstrate the ambition and leadership needed to keep the Paris Agreement’s 1.5°C limit in sight.

Mapping the climate risk to urban forests at city scale

This study uses an urban tree inventory and high-resolution climate projections to identify species and locations at risk from climate change in Melbourne. It finds that half of the tree species in Melbourne are at risk from heat stress, which could climb to two thirds in 2050.

The 1.5°C limit and risks of overshoot

This briefing looks at what the 1.5°C limit means in terms of adaptation and loss and damage for the most vulnerable countries and regions. It finds that slowing down warming is critical to buy us time to adapt and also to avoid irreversible loss and damage. Even if warming rises above 1.5°C (overshoot) we can bring it down again with ambitious emissions reductions.

Hydrologic interpretation of machine learning models for 10-daily streamflow simulation in climate sensitive upper Indus catchments

This study augments physical hydrological modeling with machine learning models to simulate surface water flows in Upper Indus water catchments in Pakistan.

Le seuil de +1,5°C et le risque de dépassement de ce seuil

Ce rapport examine ce que la limite de 1,5 °C signifie en termes d'adaptation et de pertes et dommages pour les pays et régions les plus vulnérables. Il constate qu'il est essentiel de ralentir le réchauffement pour nous donner le temps de nous adapter et pour éviter des pertes et des dommages irréversibles. Même si le réchauffement dépasse 1,5 °C, nous pouvons le faire baisser à nouveau en réduisant les émissions de manière ambitieuse.

Representing natural climate variability in an event attribution context: Indo-Pakistani heatwave of 2022

New study finds that the 2022 Indo-Pakistani heatwave was both more likely to occur and more intense due to increasing global warming – even when accounting for the effects of natural climate variability and the forced response to anthropogenic climate change.

Extreme terrestrial heat in 2023

Multiple relentless heatwaves occurred in 2023, with much of the world experiencing at least 20 more heatwave days than the 1991–2020 average. This study looks at prominent and record-breaking events around the world.

Climate impacts in northern forests

Northern forests hold around 54% of the world’s total terrestrial carbon stock and contribute more than one-third to our global terrestrial carbon sink. This report reviews the impact of human induced climate change on northern temperate and boreal forests.

Effects of idealised land cover and land management changes on the atmospheric water cycle

This study investigates how land cover and land management affects atmospheric moisture transport using global climate models. It finds that cropland expansion is generally causing a drying and reduced local moisture recycling, while afforestation and irrigation expansion generally cause wetting and increased local moisture recycling.

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A better integration of health and economic impact assessments of climate change

This study lays out how to integrate the economic repercussions of climate change on people's health with direct health impacts. The authors argue this could provide more realistic scenario projections than health studies on their own and be more useful for adaptation policy.

Kipppunkte und kaskadische Kippdynamiken im Klimasystem

Dieser im Auftrag des deutschen Umweltbundesamtes erstellte Bericht befasst sich mit Kippelementen - sensible Komponenten des Erdsystems, die bei Überschreiten kritischer Schwellenwerte (Kipppunkte) irreversiblen Veränderungen ausgesetzt werden können. Er unterstreicht, dass selbstverstärkende Mechanismen zwischen diesen Elementen zu schnellen, irreversiblen Veränderungen führen können.

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”