987. Projected Increase in Extreme Events Due to Rising Temperatures

The year 2023 marked the hottest year in recorded history, with global average temperatures rising between 1.35°C and 1.54°C above pre-industrial levels, according to the Copernicus Climate Change Service and numerous research institutions. This unprecedented record underscores the urgent need to recognize the fragile state of the Paris Agreement's 1.5°C goal, and calls for a comprehensive review of actions at all levels to avert further warming. It's important to note that the definition of temperature rise typically spans about 20 years, so a single year with an average temperature rise of 1.5°C, or even a single day exceeding 2°C, as observed, does not represent a complete derailment of the Paris Agreement's goals. However, failure to meet global emission reduction commitments could result in the Earth warming by 2.2°C to 3.4°C by the end of the century, causing profound changes in human life and the state of the planet.

In light of these projections, PNAS presents an eye-opening downscaled interactive map based on global climate model results. This map vividly illustrates the impending challenges to human health, agricultural production, and various sectors due to the projected increase in the frequency of extreme events corresponding to rising temperatures.

Deadly heat waves and humidity

Humans cool themselves mainly by sweating, but this mechanism does not work well when humidity is high. The wet bulb temperature, calculated as the combination of heat waves and humidity, is 35°C, which is considered the limit of human viability. Of course, not all people are affected in the same way, and the impact and economic losses will vary depending on the environment in which they live, their age, occupation, health status, and many other factors. In Calcutta, a city of 15 million people, the wet bulb temperature will exceed 30°C for more than 50 days under a 3°C warming, compared to 20 days now, and is expected to exceed 130 days in the hottest years, potentially affecting human life and economic activity.

Devastating droughts    

Droughts, which are expected to become more frequent with climate change, are of particular concern because of the damage they can cause to crops due to water shortages. The extent of damage depends largely on the local cropping system and the timing and duration of the drought, and even under numerically identical drought conditions, the extent of damage will vary depending on the resilience of the region in which it occurs. For example, if the temperature rises by 3°C, the probability of Cairo, Egypt, a metropolis of 20 million people, experiencing extreme drought throughout the year is expected to increase from the current 25% to 75% under a 3°C warming, and in the Nile Basin, the region's breadbasket, the already ongoing sea-level rise combined with saltwater intrusion could cause a major drought. Sea level rise and saltwater intrusion, which are already occurring in the region's breadbasket areas around the Nile, will have a tremendous impact on Egypt's agricultural production, which is dependent on food imports.

Destructive floods

Last September, torrential rains in the Libyan city of Derna caused two major dams to burst, killing more than 10,000 people. Such extreme rainfall, once thought to occur only every few hundred years, can now occur anywhere and at any time. Moreover, extreme droughts and concentrated rainfall are correlated, and there is concern that arid regions such as the African Sahel, where desertification is advancing, may experience severe flooding in the future. The question is how to protect people's livelihoods and ensure food security in such unexpected situations.

All climate change is local

The above projections, especially 3°C warming, are not inevitable. It is possible to avoid the local impacts of climate change by taking ambitious action to limit the temperature increase to less than 2°C. On the other hand, climate change may seem unfamiliar to many people because it is discussed on a global scale and numbers about global averages are bandied about. We need to move beyond abstract global averages and relate them to the extremes that people may experience in their daily lives in order to engage in policy dialogue. By relating the results of climate change projections to what is happening more locally and closer to home, we can improve the uncertainty surrounding the projections.

Reference

Where will climate change hit hardest? These interactive maps offer a telltale glimpse.　By Peter Aldhous, Data Journalist February 28, 2024. PNAS. 
https://www.pnas.org/post/update/climate-change-interactive-maps-offer-…

Contributors: Solongo TUMUR and IIYAMA Miyuki (Information Program)