839. Risk of Extreme Weather Events Under Global Warming

During this summer holiday season, reports of extreme wildfires and typhoon-related flooding came from many parts of the world. As global warming continues, the likelihood of such extreme events impacting people's lives is expected to increase, and there is an urgent need for preparedness information and a commitment to reduce greenhouse gas emissions.

A recent paper published in the journal Earth's Future uses NASA weather forecast data with 16-64 times higher spatial resolution than previously available to predict changes in indicators such as temperature, precipitation, humidity, radiation, and wind speed around the world, and to analyze the conditions under which extreme events such as heat stress and fires may occur. We analyzed the conditions under which extreme events such as heat stress and fires occur.

Previous studies have predicted an avalanche of extreme weather events with dangerous disasters under a 2°C warming compared to pre-industrial times. The current study found that variables related to climate change can interact to cause significant damage to people's lives. For example, heat stress, a combination of high temperature and humidity that poses a critical risk to human health, is projected to increase globally by the 2040s, particularly in equatorial countries, where the number of days of extreme heat stress is expected to increase, and in East Africa and the Sahel, where the number of heat stress-equivalent days has increased by one month compared to the baseline (1950-1979). In some regions, such as East Africa and the Sahel, the number of heat stress-equivalent days is projected to increase by almost one month compared to the baseline (1950-1979). The study also predicts an increase in extreme wildfire damage, noting that the Fire Weather Index (FWI), a combination of temperature, precipitation, humidity, and wind speed, could increase significantly in the Amazon, central and western North America, and the Mediterranean.

The researchers hope that accurate spatial models will enable planning and decision-making for climate change adaptation and mitigation at the local level. At the same time, the researchers call on all stakeholders to expand and accelerate the implementation of commitments to reduce greenhouse gas emissions in order to limit the warming since the Industrial Revolution to less than 2°C and, if possible, to 1.5°C in order to avoid the risks of extreme weather events described above.

Preventing more frequent heat waves and floods, as well as continued global warming, will require halting the continued rise in atmospheric greenhouse gas concentrations. Atmospheric concentrations of carbon dioxide, the primary greenhouse gas, have risen dramatically since the beginning of the Industrial Revolution in the mid-1800s, well above the historical average of 270-285 parts per million. Greta Thunberg, a world-renowned environmental activist, writes in the introductory section of her social networking account, "Born at 375 ppm”. In 2003, the year Thunberg was born, the global atmospheric concentration of carbon dioxide was 375 ppm. Twenty years later, it has reached 420 ppm.

To prevent more frequent heat waves, flooding and continued global warming, the continued rise in atmospheric greenhouse gas concentrations that contribute to global warming must be halted and reduced. According to the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC), global anthropogenic greenhouse gas emissions are estimated to be 59 Gt (gigatons) in 2019, of which 64% is carbon dioxide from fossil fuel use and industry and 11% from land use, land-use change and forestry (the remaining two being methane (18%) and nitrous oxide (4%).

The main sources of GHG emissions from agriculture, forestry and fisheries are carbon dioxide from the LULUCEF sector, methane from rice paddies and livestock, and nitrous oxide from chemical fertilizers, and efforts are needed to reduce emissions in this sector. In the LULUCF sector, the role of innovations that can improve the storage capacity of forests and soils, while minimizing land use changes due to agricultural expansion, forest fires, etc., will be crucial to achieving carbon neutrality.

※Ppm：parts per million, 1ppm=0.0001％

References

Thrasher, B., Wang, W., Michaelis, A. et al. NASA Global Daily Downscaled Projections, CMIP6. Sci Data 9, 262 (2022). https://doi.org/10.1038/s41597-022-01393-4

Park, T. et al., What Does Global Land Climate Look Like at 2°C Warming?, Earth's Future (2022). DOI: 10.1029/2022EF003330

IPCC　 AR6_WGIII_FullReport https://www.ipcc.ch/report/ar6/wg3/downloads/report/IPCC_AR6_WGIII_Full…　

NOAA　https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_annmean_gl.txt

Contributors: Solongo TUMUR and IIYAMA Miyuki (Information Program)