Tokyo Heatwaves across Asia and beyond have already broken
records this year, while the arrival of the El Nino climate
phenomenon will mean even more extreme temperatures.
Here AFP looks at how climate change produces extreme heat, how
scientists evaluate heatwaves and the risks to human health:
What is extreme heat?
Extreme heat is defined from a baseline of the average
temperature in any one location, which varies widely across the
world.
So a temperature of 25 degrees Celsius (77
degrees Fahrenheit) could be record-breaking in parts of
Canada in spring, but might be below average for the same period in
the Middle East.
What role does climate change play?
Greenhouse gases trapping heat are at the root of the problem,
said Martin Jucker, a lecturer at the University of New South Wales
Climate Change Research Centre.
Gases like carbon dioxide, methane and nitrous oxide play a
crucial role in stopping heat from being reflected or lost from our
atmosphere.
When this process is balanced, it keeps the planet at a livable
temperature.
But an unsustainable increase in the amount of greenhouse gases
in the atmosphere means more heat is being trapped, creating an
overall global warming effect and other climate anomalies.
For example, warming air holds more moisture, which produces
stronger and more frequent storms.
Overall, climate change is strengthening the duration, intensity
and geographical reach of heatwaves, scientists say.
What about human interventions?
The problem is made worse in some places by the way cities are
built the so-called heat island effect, where urban conglomerations
are warmer than surrounding rural areas.
This happens because cities with too little greenery and too
much concrete, asphalt and other building materials absorb heat and
often offer insufficient shade.
The use of cooling technologies like air conditioners creates
surging demand for energy, including the fossil fuels that are
behind the climate crisis in the first place.
Are all heatwaves linked to climate change?
To determine climate changes role in any given event, experts
use a technique called attribution science.
They simulate a world with and without climate change, using
historical and more recent measurements, or computer models.
Comparing the two then gives us a measure of how much more
likely a given extreme is under climate change, Jucker told
AFP.
Findings for over 500 events have been collected by the
organisation Carbon Brief, with most shown to have been made more
severe or more likely because of climate change.
Just a handful, including some floods, droughts and extreme
cold, have been found to have no clear link to human activity,
while in other cases experts found the evidence inconclusive.
Every heatwave in the world is now made str...
