Global Climate Change Impacts and Scenarios

Global climate change continues to reshape atmospheric, oceanic and terrestrial systems, with consequences for human societies and natural ecosystems. As greenhouse gas concentrations rise, average global temperatures have already exceeded pre-industrial levels by over 1 °C, and projections suggest warming of 1.5 °C, 2 °C or more by mid-century under differing emission pathways. Even incremental degrees of additional warming drive nonlinear changes in heatwave frequency, precipitation extremes, sea-level rise and cryosphere retreat, magnifying risks to agriculture, water resources, infrastructure and biodiversity. Scenario-based assessments integrate multiple climate model ensembles to characterise uncertainties and regional outcomes, employing techniques such as downscaling and bias correction to refine projections for impact studies. Comparative analysis of 1.5 °C versus 2 °C scenarios reveals that half-a-degree differences can halve population exposure to extreme precipitation, reduce cooling demands and limit ecological tipping points. Coupling climate trajectories with socioeconomic pathways further illuminates vulnerabilities and adaptive capacity, emphasising that robust mitigation and targeted adaptation measures are essential to safeguard human wellbeing and ecosystem services in a warming world.

Research from Nature Portfolio

Recent studies have quantified how limiting warming to 1.5 °C rather than 2 °C moderates human and environmental risks. One analysis shows that the shift from 1.5 °C to 2 °C global warming substantially increases cooling degree days across both tropical and temperate regions, underscoring the need for accelerated adaptation in energy, health and infrastructure planning. Another investigation into extreme precipitation in major land monsoon areas demonstrates that a 0.5 °C reduction in warming could lower the areal exposure to once-in-20-year rainfall events by around a quarter and reduce affected population by over a third, thereby alleviating flood risk and safeguarding agricultural productivity. A third study integrates climate and demographic projections to reveal that under high-emission scenarios, global exposure to extreme heat could increase tens-fold by 2100, but mitigation alone can prevent the vast majority of that increase, highlighting the combined importance of emissions control and social planning to reduce vulnerability.

Global Climate Change Impacts and Scenarios publication trend

The graph below shows the total number of articles in global climate change impacts and scenarios across all publications each year (not limited to Nature Index journals).

Technical terms

Cooling Degree Day: A metric summing the number of degrees by which daily mean temperature exceeds a comfort threshold, used to estimate cooling energy demand.

Downscaling: A technique for translating coarse global climate model output into finer spatial or temporal resolution suitable for regional impact analysis.

Bias Correction: A statistical adjustment applied to climate model outputs to align simulated climate variables with observed historical data.

Ensemble: A collection of multiple climate model simulations or runs used to characterise the range of possible future climate outcomes and uncertainties.

Global Warming Level (GWL): The increase in global mean surface temperature relative to a pre-industrial baseline, commonly expressed in degrees Celsius.

Time of Emergence (ToE): The point at which a climate change signal becomes distinguishable from natural variability in observational or model data.

References

1. Change in cooling degree days with global mean temperature rise increasing from 1.5 °C to 2.0 °C. Nature Sustainability (2023).
2. Reduced exposure to extreme precipitation from 0.5 °C less warming in global land monsoon regions. Nature Communications (2018).
3. Global and regional changes in exposure to extreme heat and the relative contributions of climate and population change. Scientific Reports (2017).
4. CHESS-SCAPE: high-resolution future projections of multiple climate scenarios for the United Kingdom derived from downscaled United Kingdom Climate Projections 2018 regional climate model output. Earth System Science Data (2023).
5. A Large Ensemble Global Dataset for Climate Impact Assessments. Scientific Data (2023).
6. Applying global warming levels of emergence to highlight the increasing population exposure to temperature and precipitation extremes. Earth System Dynamics (2024).