News Excerpt: 

A study in Communications Earth & Environment reports a rise in concurrent heatwaves and extreme sea level rise at coastal locations between 1998 and 2017. These events may occur five times more often between 2025 and 2049 under a high emissions scenario.

Key points related to study on concurrent heatwave and extreme sea level’ (CHWESL):

• A so-called ‘concurrent heatwave and extreme sea level’ (CHWESL) event is when a heatwave and an extreme short-term sea level rise occur at the same coastal location over the same time period. 
• This can pose a serious threat to coastal communities. 
• Yet, there has so far been little research into the characteristics and occurrences of these events.
• According to The Hong Kong Polytechnic University, China, CHWESL events worldwide between 1979 and 2017 and projected future events between 2025 and 2049 under a high emissions climate scenario (the IPCC’s SSP5-8.5 scenario). 
• • The authors only included events occurring in the extended summer season, 
    • Spanning May to September in the Northern Hemisphere,
    • November to March in the Southern Hemisphere
• Approximately 88% of the world's coastlines experienced a CHWESL event during the period 1979-2017.
• Around 39% of coastlines recorded a significant increase in the total duration of CHWESL conditions experienced over a year during 1998-2017 compared to 1979-1998, with tropical regions more likely to experience a greater increase.
  • The authors also found that if current trends in carbon emissions continue unabated,
    • CHWESL events could become up to five times more likely between 2025 and 2049.
• There is a significant association between heat wave intensity and the probability of a CHWESL event occurring, with a 1% increase in heatwave intensity associated with an approximately 2% increase in the probability of a CHWESL event.
• Global coastal areas could experience on average 38 days of CHWESL conditions each year between 2025 and 2049, 
  • an increase of 31 days compared to the historical period of 1989-2013,
  • according to projections under a high emissions climate scenario.
• CHWESL events could pose a significant threat to coastal communities, particularly from the risks of excess heat to human health.
  • Countries in tropical areas, many of which are low or middle-income countries, are likely to be the most severely affected by CHWESL events and may struggle to cope with the effects.