Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human-Induced Climate Change.

Area of Science:

• Climate Science
• Extreme Weather Events
• Environmental Science

Background:

• Extreme heat poses significant threats to human populations and ecosystems.
• Recent heat waves, particularly in 2018, have had devastating impacts, with many regions experiencing unprecedented conditions.
• The severity of heat wave impacts is amplified in areas with high human and agricultural exposure.

Purpose of the Study:

• To determine the likelihood of the 2018 Northern Hemisphere concurrent heat events occurring without human-induced climate change.
• To quantify the projected increase in high-exposure areas for heat waves with rising global temperatures.
• To emphasize the critical need for emission reductions to mitigate future heat wave risks.

Main Methods:

• Utilized Earth System Model simulations to analyze present-day climate conditions (+1°C global warming).
• Compared simulated heat extreme events with observed 2018 meteorological data.
• Applied Intergovernmental Panel on Climate Change calibrated uncertainty language to assess event attribution.

Main Results:

• It is virtually certain that the 2018 Northern Hemisphere concurrent heat events would not have occurred without human-induced climate change.
• Approximately 22% of populated and agricultural areas north of 30° latitude experienced concurrent hot temperature extremes in May-July 2018.
• Each additional +1°C of global warming is projected to increase the high-exposure area for concurrent warm and hot spells in the Northern Hemisphere by approximately 16%.

Conclusions:

• Human influence on the climate system is a primary driver of the 2018 Northern Hemisphere heat extremes.
• Urgent and substantial reductions in fossil fuel emissions are essential to avert unprecedented global heat wave impacts.
• Future warming trends indicate a significant expansion of areas vulnerable to concurrent heat spells, necessitating proactive climate mitigation strategies.