The Sparks fire during an historic heatwave in BC, Canada. A BC Wildfire Service photo June 20-21.
The world's largest study of global climate related mortality found deaths related to hot temperatures increased in all regions from 2000 to 2019, indicating that global warming due to climate change will make this mortality figure worse in the future. The international research team looked at mortality and temperature data across the world. Story here.
During the last days of June 2021, Pacific northwest areas of the
U.S. and Canada experienced temperatures never previously observed,
with records broken in many places by several degrees Celsius.
Multiple cities in the U.S. states of Oregon and Washington and the
western provinces of Canada recorded temperatures far above 40ºC (104
ºF), including setting a new all-time Canadian temperature record of
49.6ºC in the village of Lytton. Shortly after setting the record,
Lytton was largely destroyed in a wildfire [1,2].
The exceptionally high temperatures led to spikes in sudden deaths, and
sharp increases in hospital visits for heat-related illnesses and
emergency calls [3,4,5].
Heatwaves are one of the deadliest natural hazards and this heatwave
affected a population unaccustomed and unprepared for such extreme
temperatures, for instance with most homes lacking air-conditioning .
Currently available mortality estimates of at least several hundred
additional deaths are almost certainly an underestimate. The full extent
of the impact of this exceptional heat on population health will not be
known for several months.
Scientists from the US, Canada, the UK, the Netherlands, France,
Germany and Switzerland collaborated to assess to what extent
human-induced climate change made this heatwave hotter and more likely.
Using published peer-reviewed methods,
we analysed how human-induced climate change affected the maximum
temperatures in the region where most people have been affected by the
heat (45–52 ºN, 119–123 ºW) including the cities of Seattle, Portland,
and Vancouver (with well over 9 million people in their combined
Based on observations and modeling, the occurrence of
a heatwave with maximum daily temperatures (TXx) as observed in the
area 45–52 ºN, 119–123 ºW, was virtually impossible without human-caused
The observed temperatures were so extreme that they
lie far outside the range of historically observed temperatures. This
makes it hard to quantify with confidence how rare the event was. In the
most realistic statistical analysis the event is estimated to be about a
1 in 1000 year event in today’s climate.
There are two possible sources of this extreme jump
in peak temperatures. The first is that this is a very low probability
event, even in the current climate which already includes about 1.2°C of
global warming — the statistical equivalent of really bad luck, albeit
aggravated by climate change. The second option is that nonlinear
interactions in the climate have substantially increased the probability
of such extreme heat, much beyond the gradual increase in heat extremes
that has been observed up to now. We need to investigate the second
possibility further, although we note the climate models do not show it.
All numbers below assume that the heatwave was a very low probability
event that was not caused by new nonlinearities.
With this assumption and combining the results from
the analysis of climate models and weather observations, an event,
defined as daily maximum temperatures (TXx) in the heatwave region, as
rare as 1 in a 1000 years would have been at least 150 times rarer
without human-induced climate change.
Also, this heatwave was about 2°C hotter than it
would have been if it had occurred at the beginning of the industrial
revolution (when global mean temperatures were 1.2°C cooler than today).
Looking into the future, in a world with 2°C of
global warming (0.8°C warmer than today which at current emission levels
would be reached as early as the 2040s), this event would have been
another degree hotter. An event like this – currently estimated to occur
only once every 1000 years, would occur roughly every 5 to 10 years in
that future world with 2°C of global warming.
In summary, an event such as the Pacific Northwest 2021 heatwave is
still rare or extremely rare in today’s climate, yet would be virtually
impossible without human-caused climate change. As warming continues, it
will become a lot less rare.
Our results provide a strong warning: our rapidly warming climate is
bringing us into uncharted territory that has significant consequences
for health, well-being, and livelihoods. Adaptation and mitigation are
urgently needed to prepare societies for a very different future.
Adaptation measures need to be much more ambitious and take account of
the rising risk of heatwaves around the world, including surprises such
as this unexpected extreme. Deaths from extreme heat can be dramatically
reduced with adequate preparedness action. Heat action plans that
incorporate heatwave early warning systems can strengthen the resilience
of cities and people. In addition, longer-term plans are needed to
modify our built environments to be more adequate for the hotter climate
that we already experience today and the additional warming that we
expect in future. In addition, greenhouse gas mitigation goals should
take into account the increasing risks associated with unprecedented
climate conditions if warming would be allowed to continue
The heatwave considered in this study is linked to a slow-moving
strong high pressure system, sometimes called Omega-blocking or “heat
dome”, which brings descending and thus warm and dry air, as well clear
skies, further heating the near-surface air. This high pressure system
also reached record levels in terms of its strength, measured as the
“thickness” of the lower part of the atmosphere, the so-called troposphere.
The pressure values observed in the very strong blocking anticyclone
are comparable to those observed in other parts of the world in recent
heatwaves. The “Omega” blocking pattern is typically associated with
heatwaves in this region. While the pressure system was record-breaking
in its values, it was far less unusual compared to climatology than the
associated extreme temperatures. Recent research suggests that climate
change increases the chances for such stagnant high pressure systems in
summer through weakening of the summer jet stream. As of yet, it is
unclear if, and to what extent, such long-term dynamical changes play a
role in this event.
An important feature of this extreme heatwave is that it occurred
following a very dry spring over the Western U.S., so the absence of
evaporative cooling could be an important factor in the exceptional
temperatures observed. However, the northern part of the region impacted
by this heatwave experienced wet anomalies in the weeks and months
preceding the heat. Anticyclonic subsidence, and downslope winds were
also present, and probably acted as additional heating factors. Overall,
it is difficult at this stage to assess the extent to which these
factors either in isolation or combined provide a good explanation of
why the observed temperatures were so much higher than anything ever
recorded in this part of the world. Hence, more research is needed to
understand the processes as well as potential influence of human-caused
climate change on them.
Here we provide a first estimate of the role of climate change on the
extreme temperatures measured in the Pacific Northwest. We analyse the
maximum daily temperatures as these are relevant to the impact of the
event. While the minimum temperatures are also important for health
impacts, we used only one index to keep the assessment straightforward.
In this rapid study, we do not analyse the impact that human-caused
climate change may have on specific aspects leading to the observed
synoptic situation. We ask whether and to what extent human-caused
climate change altered the likelihood and intensity of the analysed
event. Specifically we analyse (1) how the likelihood of the yearly
maximum temperature to be as high or higher than observed in June 2021
has changed and (2) how much less severe a heatwave with the same return
period would have been in a world without human-caused climate change.
It is important to highlight that, because the temperature records of
June 2021 were very far outside all historical observations, determining
the likelihood of this event in today’s climate is highly uncertain.
All numbers shown assume that the heatwave was a very low probability
event (about 1 in 1000 years) that was not caused by new nonlinearities.
As in previous analyses,
we only give a lower bound of the estimate of the influence of climate
change on the change in probability of the event as the best estimate
and upper bound are very ill-defined for extreme heat.
Based on this first rapid analysis, we cannot say whether this was a
so-called “freak” event (with a return time on the order of 1 in 1000
years or more) that largely occurred by chance, or whether our changing
climate altered conditions conducive to heatwaves in the Pacific
Northwest, which would imply that “bad luck” played a smaller role and
this type of event would be more frequent in our current climate.
In either case, the future will be characterized by more frequent,
more severe, and longer heatwaves, highlighting the importance of
significantly reducing our greenhouse gas emissions to reduce the amount
of additional warming.
The latest heat-related death numbers are alarming, yet they are
likely a severe undercount and the real toll will only become clear
after mortality statistics are reviewed for the role of heat in
exacerbating underlying conditions.
Butterflies such as the great purple hairstreak, Atlides halesus, are in decline in the warming American West according to community surveys. PHOTO: JEFFREY GLASSBERG/NORTH AMERICAN BUTTERFLY ASSOCIATION
One of several steel power pylons toppled in an historic wind, snow and ice storm which swept through eastern Manitoba about a year ago. It left thousands without power in what was described as the worst power outage in the history of Manitoba Hydro. Damages are expected to exceed 100 million dollars. A Manitoba Hydro photo.
Even if human-induced greenhouse gas (GHG) emissions can be reduced to zero, global temperatures may continue to rise for centuries afterwards, according to a simulation of the global climate published in Scientific Reports.
Jorgen Randers and Ulrich Goluke modelled the effect of different greenhouse gas emission reductions on changes in the global climate from 1850 to 2500. They also created projections of global temperature and sea level rises.
What do they show? Under conditions where manmade greenhouse gas emissions peak during the 2030s, then decline to zero by 2100, global temperatures will be 3°C warmer and sea levels 3 metres higher by 2500 than they were in 1850. Where all such emissions are reduced to zero during the year 2020 here's the scenario the models portray.
After an initial decline, global temperatures will still be around 3°C warmer and sea levels will rise by around 2.5 metres by 2500, compared to 1850. Global temperatures could continue to increase after emissions have reduced, as continued melting of Arctic ice and carbon-containing permafrost may increase the levels of water vapour, methane and carbon dioxide in the atmosphere. Melting of Arctic ice and permafrost would also reduce the area of ice reflecting heat and light from the sun.
To prevent the projected temperature and sea level rises, the authors suggest that all GHG emissions would have had to be reduced to zero between 1960 and 1970. To prevent global temperature and sea level rises after greenhouse gas emissions have ceased, and to limit the potentially catastrophic impacts of this on Earth’s ecosystems and human society, at least 33 gigatonnes of carbon dioxide would need to be removed from the atmosphere each year from 2020 onwards through carbon capture and storage methods.
The Athabasca glacier in Jasper National Park, Canada. Already a shadow of its former self, many fear it will be gone altogether within a generation. A 2020 photo by Ethan Sahagun.
Nature reserves will be affected by future climate change in very different ways - especially in the tropics. A new study drawing attention to this fact, raises even more fears for wildlife species. It's based on forecasts for more than 130,000 nature reserves worldwide. Story here.
A table iceberg in the Norwegian Arctic. Such icebergs are rare as they calve from shelf ice, which is also rare. They're normally a typical form of iceberg in the Antarctic. This one is about 12m high and about half the size of a soccer field. Photo by Andreas Weith.
The eastern Arctic Ocean's winter ice grew less than half as much as normal during the past decade, due to the growing influence of heat from the ocean's interior, researchers have found. Story here.
Permafrost Slide at Big Fox Lake, Ontario, Canada - 2015. A Creative Commons photo by MIKOFOX.
For thousands of years, so-called "permafrost peatlands" in Earth's Northern Hemisphere have been cooling the global climate. They’ve done it by trapping large amounts of carbon and nitrogen which would otherwise escape into the air as harmful greenhouse gases. More recently however, scientists have observed, they've been melting due to manmade global heating. As they melt, they're releasing large amounts of substances like methane - a potent greenhouse gas - into the air. But, without proper maps, it's been hard for scientists to get a handle on the degree to which this might be happening - until now. New ones drawn up using thousands of field observations, show; Permafrost peatlands cover a vast area of almost four million square kilometres. And, to quote from the study, "Under future global warming scenarios, half to nearly all of peatland permafrost could be lost this century.” This means their age-old role, mostly as net “sinks,” keeping harmful greenhouse gases in the ground, would transform to a net source of atmospheric carbon, primarily methane.
A permafrost "slump" in Alaska. A USGS photo.
The research concludes that, “Although northern peatlands are currently a source of global cooling, permafrost thaw attributable to anthropogenic climate warming may convert peatlands into a net source of warming." The findings were published recently in PNAS, the proceedings of the National Academy of Sciences (US). But the impact of the nitrogen trapped in these fields cannot be underestimated, either. A separate study, also published in PNAS about three years ago, reveals, "Some 67 billion tons of it, accumulated thousands of years ago, could now become available for decomposition, leading to the release of nitrous oxide (N2O) to the atmosphere. N2O is a strong greenhouse gas, almost 300 times more powerful than CO2 for warming the climate. Although carbon dynamics in the Arctic are well studied, the fact that Arctic soils store enormous amounts of nitrogen has received little attention so far. We report that the Arctic may become a substantial source of N2O when the permafrost thaws, and that N2O emissions could occur from surfaces covering almost one-fourth of the entire Arctic."
This summer, the world is experiencing record hot temperatures: A weather station in Death Valley, California, clocked one of the hottest temperatures ever observed on Earth. Simultaneously, the coronavirus pandemic’s devastating mortality impact and economic fallout are demanding society prioritize public health like never before. Details here.
An emaciated moose in Riding Mtn. National Park, Canada.
A PinP photo. All but one of 459 species have traits making them vulnerable to rising temperatures, study finds. Story here.
To quote from the initial study in Nature, Climate Change: "Climate change is a threat to ecosystems and biodiversity globally and has emerged as a driver of observed and potential species decline and extinction. Government laws and policies should play a vital role in supporting climate change adaptation for imperilled species, yet imperilled species protections have been critiqued as insufficient in Australia, Canada and Europe." PinP
The frequency of downpours of heavy rain—which can lead to flash floods, devastation, and outbreaks of waterborne disease—has increased across the globe in the past 50 years, research led by the University of Saskatchewan (USask) has found. Story here.