Pre industrial temperature levels
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Understanding Pre-Industrial Temperature Levels and Their Impact on Climate Targets
Definition and Importance of Pre-Industrial Baseline
The term "pre-industrial levels" is crucial in climate discussions, particularly in the context of the Paris Agreement, which aims to limit global temperature rise to well below 2°C, and ideally to 1.5°C, above these levels. However, the exact definition of "pre-industrial" remains ambiguous, leading to significant implications for climate policy and mitigation strategies Schurer2017Schurer2018Hawkins2017.
Variability in Pre-Industrial Temperature Baselines
Research indicates that pre-industrial temperatures have been highly variable over the past millennia. The commonly used reference period of 1850-1900, which marks the end of the Little Ice Age (LIA), is considered one of the coldest phases in the last 10,000 years. This period may not be the most representative baseline for pre-industrial temperatures. Some studies suggest that the temperature levels from 1940-1970 might better reflect the average pre-industrial temperatures of the past two millennia .
Implications for Climate Targets
The choice of pre-industrial baseline significantly affects the probability of exceeding the 1.5°C and 2°C thresholds. For instance, under the strongest mitigation scenario (RCP2.6), the likelihood of crossing the 1.5°C threshold by the end of the century varies from 61% to 88%, depending on the baseline used. In scenarios with no mitigation (RCP8.5), both thresholds are almost certain to be exceeded by mid-century, regardless of the baseline definition .
Health Risks Associated with Temperature Increases
The health risks associated with global warming are projected to be significantly higher at a 2°C increase compared to a 1.5°C increase above pre-industrial levels. These risks include higher exposure to extreme temperatures, poor air quality, undernutrition, and vector-borne diseases. The burden of these health risks underscores the importance of stringent climate targets and timely adaptation interventions .
Human Contributions to Observed Warming
Human activities have been a major driver of the observed warming since the pre-industrial period. Climate model simulations indicate that anthropogenic forcings have caused 0.9 to 1.3°C of warming in global mean near-surface air temperature from 2010 to 2019, relative to the 1850-1900 baseline. This highlights the substantial human influence on climate and the urgency of reducing greenhouse gas emissions to meet the Paris Agreement goals .
Recommendations for Future Assessments
To improve the accuracy and policy relevance of climate targets, some researchers recommend using a modern baseline, such as the period from 1720-1800, which might offer a more stable reference point. This approach could reduce uncertainties and provide clearer guidance for climate mitigation efforts .
Conclusion
The definition of pre-industrial temperature levels is a critical factor in climate science and policy. Variability in these baselines can significantly influence the perceived urgency and strategies for meeting global temperature targets. Understanding and standardizing this baseline is essential for effective climate action and for minimizing the health and environmental risks associated with global warming.
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