Northern Hemisphere’s Extreme Heatwave In 2018 Impossible Without Climate Change

Northern Hemisphere’s Extreme Heatwave In 2018 Impossible Without Climate Change

Last summer’s unprecedented northern-hemisphere heatwave “could not have occurred without human-induced climate change”, a new study concludes.

Scientists are “virtually certain” that the three-month event – which saw temperature records broken from Belfast to Montreal and wildfires in places such as the Arctic circle, Greece and California – could not have happened in a world without human-caused greenhouse gas emissions.

The study also finds that summer heatwaves on the scale of that seen in 2018 could occur every year if global temperatures reach 2C above pre-industrial levels. If global warming is limited to 1.5C – the international aspirational limit – such heatwaves could occur in two of every three years.

The findings mirror recent research suggesting that the extreme heat seen in Japan in 2018, in which more than 1,000 people died, could not have occurred without climate change.

Both studies are the latest in “attribution science”, a field that uses modern techniques to detect the “fingerprint” of climate change on extreme-weather events.

Summer scorcher

Last summer’s unprecedented northern-hemisphere heatwave dominated frontpages. The extreme heat lasted for months and broke temperature records simultaneously across North America, Europe and Asia.

Among its impacts, the heatwave caused crop failures across Europe, fanned wildfires from Manchester in the UK to Yosemite National Park in the US and exposed more than 34,000 people to power outages in Los Angeles as the grid experienced an unprecedented demand for air conditioning.

As the heat continued to wreak havoc at the end of July, scientists released a rapid assessment finding that climate change made the hot conditions seen in Europe up to five times more likely to occur.

This was followed later by preliminary analysis from the UK’s Met Office in December which found that the heat experienced by the UK was made up to 30 times more likely by climate change.

And, in May, a study found that the heatwave in Japan – one of the worst affected countries – could not have happened at all without human-caused global warming.

The new paper, published in the journal Earth’s Future, is the first to assess the extent to which climate change could have boosted the odds of a heatwave on the same scale of that seen in 2018 across the entire northern hemisphere.

The results reveal that last summer’s northern-hemisphere heatwave was “extraordinary”, says study lead author Dr Martha Vogel, a climate extremes researcher from ETH Zurich. She tells Carbon Brief:

“We find these 2018 northern-hemispheric concurrent heat events could not have occurred without human-induced climate change. We are now in a climate where large areas can be affected simultaneously by extreme temperatures.”

Finding a fingerprint

For the analysis, the scientists first had to get a picture of the overall scale of last summer’s heatwave.

Using temperature data, they found that, on average, 22% of the northern hemisphere experienced “extremely hot” days simultaneously from May to June.

(The authors only considered land that was either densely populated or used for agricultural production. “Extremely hot” days were considered to be days when temperatures exceeded the 90th percentile of daily temperatures from 1958-88.)

The chart below gives an idea how the average fraction of land experiencing extreme heat in the northern hemisphere from May to July has changed from 1958 to today. On the chart, stars pinpoint the four largest northern-hemisphere heatwave events on record.

Northern Hemisphere’s Extreme Heatwave In 2018 Impossible Without Climate Change

The average fraction of land experiencing extreme heat in the northern hemisphere from May to July. (Only densely populated and agricultural land is considered.) Stars pinpoint the four largest northern-hemisphere heatwave events on record. Source: Vogel et al. (2019)

The researchers then used climate models to study how often heatwaves on this scale are expected to happen in today’s world and in a hypothetical world without climate change.

To do this, the researchers produced three sets of simulations. The first set of simulations mirrored the conditions of today’s climate, including the influence of human-caused climate change.

The second set of simulations mirrored conditions from 1958-88, a time when the world had already warmed by 0.28C, according to the researchers. The third set of simulations mirrored “pre-industrial” conditions, a time before human-caused global warming.

The researchers then studied the simulations to see how often heatwaves on the same scale to that seen in 2018 occur under the various climate conditions.

The findings show that heatwaves on the same scale as that seen in 2018 have around a one-in-six chance of occurring in today’s climate. In contrast, in the simulations from 1955-88, such heatwaves had no chance of occuring.

This led the researchers to conclude that it is “virtually certain” that the 2018 northern-hemisphere heatwave could not have happened without climate change. Vogel explains:

“‘Virtually certain’ means that the probability that the event could have only occurred due to climate change is more than 99%.”

The language reflects the uncertainty guide used by the Intergovernmental Panel on Climate Change (IPCC).

Furnace forecast

The researchers also used climate models to make projections about the likelihood of heatwaves on the same scale as 2018 or larger occurring under a range of temperature scenarios.

They found that, if global temperatures are limited to 1.5C, such heatwaves could occur in around two of every three years – or a 65% probability of occurring in any one year. If temperatures reach 2C, such heatwaves could occur every year (97% probability).

This is demonstrated on the charts below, which show the probability of heatwaves on the same spatial scale to that seen in 2018 or larger occurring in the northern hemisphere under 1.5C (top) and 2C (bottom). On the chart, the dashed line shows the spatial scale of the 2018 northern-hemisphere heatwave.

Northern Hemisphere’s Extreme Heatwave In 2018 Impossible Without Climate Change

The probability, in a given year, of heatwaves on the same spatial scale to that seen in 2018 or larger occurring in the northern hemisphere under 1.5C (top) and 2C (bottom) of global warming. The dashed line shows the spatial scale of the 2018 northern-hemisphere heatwave. The box plot shows the average probability under each temperature and she spread of results. Source: Vogel et al. (2019)

The findings reinforce the need to strengthen efforts to meet the 1.5C target, Vogel says:

“If heatwaves occur in densely populated regions, this will have strong impacts on human health – particularly in regions where the expanding concurrent hot-days area is compounded by population increases. Hence, strong mitigation efforts are required to avoid future simultaneous heat-related impacts.”

The research represents “an important” step forward in our understanding of how climate change impacted last year’s northern-hemisphere heatwave, says Prof Peter Stott, a leading attribution scientist from the Met Office Hadley Centre, who was not involved in the study. He tells Carbon Brief:

“The authors come to the striking conclusion that we have entered a new climate regime in which the occurrence of extraordinary global-scale heatwaves cannot be explained without human-induced climate change. This finding is consistent with many other studies also reporting a rapidly escalating risk of such hot extremes.”

This Article Originally Appeared On Carbon Brief

Related Books

Climate Change: What Everyone Needs to Know

by Joseph Romm
0190866101The essential primer on what will be the defining issue of our time, Climate Change: What Everyone Needs to Know® is a clear-eyed overview of the science, conflicts, and implications of our warming planet. From Joseph Romm, Chief Science Advisor for National Geographic's Years of Living Dangerously series and one of Rolling Stone's "100 people who are changing America," Climate Change offers user-friendly, scientifically rigorous answers to the most difficult (and commonly politicized) questions surrounding what climatologist Lonnie Thompson has deemed "a clear and present danger to civilization.". Available On Amazon

Climate Change: The Science of Global Warming and Our Energy Future second edition Edition

by Jason Smerdon
0231172834This second edition of Climate Change is an accessible and comprehensive guide to the science behind global warming. Exquisitely illustrated, the text is geared toward students at a variety of levels. Edmond A. Mathez and Jason E. Smerdon provide a broad, informative introduction to the science that underlies our understanding of the climate system and the effects of human activity on the warming of our planet.Mathez and Smerdon describe the roles that the atmosphere and ocean play in our climate, introduce the concept of radiation balance, and explain climate changes that occurred in the past. They also detail the human activities that influence the climate, such as greenhouse gas and aerosol emissions and deforestation, as well as the effects of natural phenomena.  Available On Amazon

The Science of Climate Change: A Hands-On Course

by Blair Lee, Alina Bachmann
194747300XThe Science of Climate Change: A Hands-On Course uses text and eighteen hands-on activities to explain and teach the science of global warming and climate change, how humans are responsible, and what can be done to slow or stop the rate of global warming and climate change. This book is a complete, comprehensive guide to an essential environmental topic. Subjects covered in this book include: how molecules transfer energy from the sun to warm the atmosphere, greenhouse gases, the greenhouse effect, global warming, the Industrial Revolution, the combustion reaction, feedback loops, the relationship between weather and climate, climate change, carbon sinks, extinction, carbon footprint, recycling, and alternative energy. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

EVIDENCE

Why You Shouldn't Use
Why You Shouldn't Use "Weather" And "Climate" Interchangeably
by Jennifer Fitchett
As January 2019 entered its third week, huge swathes of the US are blanketed with snow, and winter storm warnings were…
Evidence Shows Warming Forces World Of Ice Into Retreat
New Evidence Shows Warming Forces World Of Ice Into Retreat
by Tim Radford
New evidence from the air, space, atmospheric chemistry and old records is testament to global warming impacts on the…
Why We Know California Wildfires Will Get Even Worse
Why We Know California Wildfires Will Get Even Worse
by Kevin Stacey
The severity of wildfires in the Sierra Nevada region of California has been sensitive to changes in climate over the…
New Research Shows How Much Methane Goes From The Ocean To The Atmosphere Each Year
New Research Shows How Much Methane Goes From The Ocean To The Atmosphere Each Year
by Lindsey Valich
New research uses data science to determine how much methane goes from the ocean and into the atmosphere each year.
How Much Of Climate Change Is Natural? How Much Is Man-made?
How Much Of Climate Change Is Natural? How Much Is Man-made?
by Mark New
As someone who has been working on climate change detection and its causes for over 20 years I was both surprised and…
Why Some People Still Think Climate Change Isn't Real
Why Some People Still Think Climate Change Isn't Real
by David Hall
At its heart, climate change denial is a conflict between facts and values. People deny the climate crisis because, to…
Europe's Most Iconic Mountain Is A Climate Change Warning
by ABC News
ABC News' James Longman reports from Mont Blanc, where a glacier on the Italian side of the mountain is breaking apart…
Science Counts Humankind’s Carbon Output
Science Counts Humankind’s Carbon Output
by Tim Radford
We leave the planet’s volcanos far behind on greenhouse gas emissions: humankind’s carbon output can exceed theirs by…

LATEST VIDEOS

South Africans Are Feeling The Heat In More Ways Than One
by eNCA
Load-shedding combined with soaring temperatures are a bad combination.
Why Uncertainty Can Actually Boost Trust In Climate Science
Why Uncertainty Can Actually Boost Trust In Climate Science
by Melissa De Witte
The more specific climate scientists are about the uncertainties of global warming, the more the American public trusts…
How World Conflicts Are Influence By The Changing Climate
How World Conflicts Are Influence By The Changing Climate
by John Vidal
The relationship between a heating planet and violent clashes is complex — and critical. “This is where I keep my…
Emergency Medicine For Our Climate Fever
by Kelly Wanser
As we recklessly warm the planet by pumping greenhouse gases into the atmosphere, some industrial emissions also…
What Extinction Rebellion climate activists are demanding from governments
by Democracy Now!
More than 700 climate activists were arrested in 60 cities worldwide in a global effort aimed at urging governments to…
Can Nature Repair The Planet From Climate Change?
by The Economist
A closer look at one of the most familiar responses offered to the climate crisis.
How Climate Change Is Threatening Homes In Mumbai
by South China Morning Post
Lowland cities and islands such as the Indian city of Mumbai may face increasingly frequent floods and storms
This is Not A Drill: 700+ Arrested as Extinction Rebellion Fights Climate Crisis With Direct Action
by Democracy Now!
More than 700 people have been arrested in civil disobedience actions as the group Extinction Rebellion kicked off two…

LATEST ARTICLES

How Divergent Goals Hinder The Fight Of The Climate Crisis
How Divergent Goals Hinder The Fight Of The Climate Crisis
by Pascale Dufour
Nearly half a million people demonstrated in Montréal to demand climate action on Sept. 27. It was one of the largest…
Why You Shouldn't Use
Why You Shouldn't Use "Weather" And "Climate" Interchangeably
by Jennifer Fitchett
As January 2019 entered its third week, huge swathes of the US are blanketed with snow, and winter storm warnings were…
South Africans Are Feeling The Heat In More Ways Than One
by eNCA
Load-shedding combined with soaring temperatures are a bad combination.
Iowa's Farmers – And American Eaters – Need A National Discussion On Transforming Us Agriculture
We Need A National Discussion On Transforming Agriculture
by Lisa Schulte Moore
Iowa’s first-in-the-nation caucuses bring the state a lot of political attention during presidential election cycles.
Can We Deal With The Climate Crisis Without Having A Financial Chaos?
Can We Deal With The Climate Crisis Without Having A Financial Chaos?
by Geoff Dembicki
Communities face a tricky dilemma as climate changes: How to prepare for impacts without scaring away homeowners and…
Should Science Must Be Mobilized Like World War Ii To Fight The Climate Crisis
Should Science Must Be Mobilized Like World War Ii To Fight The Climate Crisis
by Tom Oliver
We’ve all but won the argument on climate change. The facts are now unequivocal and climate denialists are facing a…
The IEA Projects Global Renewable Energy Capacity to Rise by 50% in next 5 Years
The IEA Projects Global Renewable Energy Capacity to Rise by 50% in next 5 Years
by Jessica Corbett
However, the deployment of renewables "still needs to accelerate if we are to achieve long-term climate, air quality,…
Evidence Shows Warming Forces World Of Ice Into Retreat
New Evidence Shows Warming Forces World Of Ice Into Retreat
by Tim Radford
New evidence from the air, space, atmospheric chemistry and old records is testament to global warming impacts on the…