Heat Extremes Persist Despite Net Zero Goals
The relentless rise in greenhouse gas emissions by human activities has accelerated global warming, exacerbating high-impact heat events globally over the last seven decades. These heat extremes—including heatwaves—wreak havoc on infrastructure, compromise ecosystems, and can tragically lead to loss of life.
Recently, temperatures have reached unprecedented levels as estimates indicate the world may not meet the global objective of limiting the temperature increase to below 1.5 degrees Celsius above pre-industrial levels. Exceeding this threshold poses escalating threats to health, food and water security, as well as economic growth.
To avert these threats, carbon dioxide emissions must be reduced sufficiently for natural processes like the land and ocean absorption to equalize emissions, achieving what is termed Net Zero. This target aims for a complete balance of emissions by 2050, a goal pledged by multiple nations worldwide.
However, will the achievement of Net Zero have a palpable effect in moderating heat extremes, particularly across the vulnerable African continent? As climate researchers exploring potential futures of climate change post-Net Zero, we conducted experiments with climate models simulating a transition to Net Zero on a global scale. The findings indicate that while a decrease in heat intensity across many parts of the world might occur, results vary significantly by region.
Southern Africa, in particular, presents an uncertain scenario. Since the mid-20th century, this region has experienced significant temperature increases. It is particularly susceptible to extreme and destructive events stemming from global warming, like Cape Town’s “Day Zero” drought.
Grasping how temperature extremes may transform post-Net Zero is crucial for informing future planning and policymaking. Notably, even with greenhouse gas emissions curtailed, diverse regions across the globe could still experience pronounced effects of climate change.
This knowledge empowers governments and international entities to prepare for a spectrum of potential outcomes. Greenhouse gases that remain in the atmosphere when not absorbed by natural processes contribute to the greenhouse effect, perpetuating Earth’s warming.
Land experiences a faster rise in average temperatures compared to the oceans, resulting in pronounced regional hotspots. Among these are southern Africa, the Amazon, and the Mediterranean. Scientists have been striving for decades to decipher regional heat extreme changes in these hotspots, with most studies historically focused on uninterrupted emissions scenarios.
In our analysis, we employed climate models to envisage changes in heat extremes in a Net Zero future, contrasting heat extremes a century post-Net Zero against those at the point of achieving Net Zero. This approach mirrors comparisons between current warming dynamics and pre-industrial times.
The projections suggest a decline in heat extremes over much of the land. However, substantial regional variations remain. Our objective was to pinpoint causes for these stark differences in temperature extremes after Net Zero. We paid particular attention to southern Africa, a region grappling with unpredictable changes and significant impacts from extreme heat.
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Some of our models predict that the “hotspot” phenomenon over southern Africa, spurred by global warming, might reverse post-Net Zero. Conversely, other models indicate minimal alteration in heat extreme intensity in the region despite achieving Net Zero.
The models also vary on precipitation, with some forecasting increased rainfall—particularly in southernmost areas—and others predicting drying trends. These differences will significantly impact the local climate. Moist soil from rainfall tends to cool land-based temperatures, while evaporation also contributes to cooling.
Our models are crafted by various international agencies with unique methodologies, resulting in discrepancies in future climate projections. This variation is evident in our study, emphasizing the critical role regional precipitation and land surface conditions might play in future temperature extremes.
Scientifically, accumulating more data on climate responses to Net Zero remains invaluable. Simulation models are instrumental in assessing potential weather pattern disruptions. They help ascertain whether the planet is nearing irreversible tipping points from climate change-induced damage.
For policymaking, the existing uncertainty in model predictions for local Net Zero responses should not deter commitments. Policymakers should leverage the research on post-Net Zero climate shifts to prepare for the myriad potential outcomes.
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