Climate Code Red: What we learned about the climate system in 2017 that should send shivers down the spines of policy makers

by David Spratt, Climate Code Red, January 15, 2018

Much of what happened in 2017 was predictable: news of climate extremes became, how can I put it … almost the norm. There was record-breaking heat on several continents, California’s biggest wildfire (extraordinarily in the middle of winter), an ex-tropical cyclone hitting Ireland (yes, Ireland) in October, and the unprecedented Hurricanes Harvey, Irma and Maria that swept through the Atlantic in August. The US government agency, the NOAA, reported that there were 16 catastrophic billion-dollar weather/climate events in the USA during 2017.

And 2017 “marks the first time some of the (scientific) papers concluded that an event could not have occurred — like, at all — in a world where global warming did not exist. The studies suggested that the record-breaking global temperatures in 2016, an extreme heat wave in Asia and a patch of unusually warm water in the Alaskan Gulf were only possible because of human-caused climate change,” Reuters reported.

At both poles, the news continues to be not good. At the COP23 in Bonn, Pam Pearson, Founder and Director of the International Cryosphere Climate Initiative, warned that the cryoshere is becoming “an irreversible driver of climate change.” She said that most cryosphere thresholds are determined by peak temperature, and the length of time spent at that peak, warning that “later, decreasing temperatures after the peak are largely irrelevant, especially with higher temperatures and longer duration peaks.” Thus “overshoot scenarios,” which are now becoming the norm in policy-making circles (including all 1.5 °C scenarios) hold much greater risks.

As well, Pearson said that 2100 is a misleading and minimizing measure of cryosphere response: “When setting goals, it is important to look to new irreversible impacts and the steady state circumstances. The end of the century is too soon to show that before but inevitable response especially for sea level rises.” Pearson added that: “What keeps cryosphere scientists up at night are irreversible thresholds, particularly West Antarctica and Greenland. The consensus figure for the irreversible melting of Greenland is at 1.6 °C.”

So what did we learn about the climate system in 2017? Here’s three that stand out, that should send shivers down the spines of policy makers. 

1.  2017 was the second hottest year on record and the hottest non-El Nino year on record

Whilst not all sources have yet released data on annual warming for last year, the Copernicus Climate Change Service, the first major international weather agency to report global 2017 temperatures, said they averaged 1.2 °C above pre-industrial times. 2017 was slightly cooler than the warmest year on record, 2016, and warmer than the previous second warmest year, 2015, Reuters reported.

Other organisations have unofficial figures which either agree with this assessment, or say that 2017 has tied with 2015. And last year was Australia's third-warmest year on record.

It is no surprise that the last three years have been the hottest on the instrumental record. What is remarkable is that 2017 was as hot, or hotter than 2015, because 2015 and 2016 were both El Nino years, and the evidence shows that El Nino years are, on average, about 0.15 °C warmer than La Nina years.In fact, a remarkably hot 2017 crushed the old record for hottest non-El Niño year (2014) by an astounding 0.17 °C.

The underlying temperature trend is being driven by continuing high levels of climate pollution: The UN says carbon dioxide levels grew at record pace in 2016. The atmospheric carbon dioxide  averaged 403.3 parts per million (ppm) over the year, up from 400 ppm in 2015. The growth rate was 50% faster than the average over the past decade.

And global carbon emissions are headed up again after three years in which human-caused emissions appeared to be leveling off. A 2% increase is projected overall, with the highest rise coming in China, according to new research presented at the climate talks in Bonn.

In 2017, we also learned that there was no pause in global warming: the so-called ’slow down' in climate change between 1998 and 2012 was caused by a lack of data from the Arctic.

2. It is likely to get hotter than we think

Two significant pieces of work released towards the end of 2017 suggest that warming is likely to be greater than the projections of the Intergovernmental Panel on Climate Change (IPCC), on which climate policy-making and carbon budgets are generally based. 

This is because what is called Equilibrium Climate Sensitivity (ECS), an estimate of how much the planet will warm for a doubling in the level of greenhouse gases, is higher than the median of the IPCC’s modelling analysis. 

In “Greater future global warming inferred from Earth’s recent energy budget” published in Nature in December 2017, Brown and Caldeira compared the performance of a wide range of climate models (raw model projections) with recent observations (especially on the balance of incoming and outgoing top-of-the-atmosphere radiation that ultimately determines the Earth’s temperature), in order to assess which models perform best.

The models that best capture current conditions (the “observationally-informed” models) produce 15% more warming by 2100 than the IPCC suggests, hence reducing the “carbon budget” by around 15% for the 2C target.

 For example, they find the warming associated by the IPCC with RCP 4.5 emissions scenario would in fact “follow the trajectory previously associated with (higher emissions) RCP 6.0” scenario. 

They also find that the observationally-informed ECS prediction has a mean value of 3.7 °C (for a doubling of the atmospheric greenhouse gas level), compared to 3.1 °C used in raw models, and in the carbon budget analyses widely used by the IPCC, the UN and at climate policy conferences.

In “Well below 2C: Mitigation strategies for avoiding dangerous to catastrophic climate changes,” published in September 2017, Xu and Ramanathan look at what are called the “fat tail” risks. These are the low-probability, high-impact (LPHI) consequences (“fat tails”) of future emission scenarios; that is, events with a 5% probability at the top end of the range of possible outcomes. 

These “top end” risks are more likely to occur than we think, so “it is important to use high-end climate sensitivity because some studies have suggested that 3D climate models have underestimated three major positive climate feedbacks: positive ice albedo feedback from the retreat of Arctic sea ice, positive cloud albedo feedback from retreating storm track clouds in mid-latitudes, and positive albedo feedback by the mixed-phase (water and ice) clouds.” 

When these are taken into account, the researchers find that the ECS is more than 40% higher than the IPCC mid-figure, at 4.5-4.7 °C. And this is without taking into account carbon cycle feedbacks (such as melting permafrost and the declining efficiency of forests carbon sinks), and increase methane emissions from wetlands, which together could add another 1 °C to warming be 2100. 

This work complements other recent work which also suggests a higher climate sensitivity:

• Fasullo and Trenberth found that the climate models that most accurately capture observed relative humidity in the tropics and subtropics and associated clouds were among those with a higher sensitivity of around 4 °C.

• Zhai et al. found that seven models that are consistent with the observed seasonal variation of low-altitude marine clouds yield an ensemble-mean sensitivity of 3.9 °C. 

• Friedrich et al. show that climate models may be underestimating climate sensitivity because it is not uniform across different circumstances, but in fact higher in warmer, inter-glacial periods (such as the present) and lower in colder, glacial periods. Based on a study of glacial cycles and temperatures over the last 800,000 years, the authors conclude that in warmer periods climate sensitivity averages around 4.88 °C. Professor Michael Mann, of Penn State University, says the paper appears "sound and the conclusions quite defensible."

• Lauer et al. found that climate models that most accurately simulate recent cloud cover changes in the east Pacific point to an amplifying effect on global warming and thus a more sensitive climate. 

And the bottom line?  If this work is correct, then the pledges made under the Paris Accord would not produce warming of around 3 °C as is widely discussed, but a figure closer to and even above 4 °C. And the total carbon budget would a quarter smaller than is generally accepted, or even less.

3. Climate models under-estimate future risks

This year, the Breakthrough Centre for Climate Restoration in Melbourne, published What Lies Beneath, on the scientific understatement of climate risks. The report found that human-induced climate change is an existential risk to human civilization, yet much climate research understates climate risks and provides conservative projections. Reports from the Intergovernmental Panel on Climate Change that are crucial to climate policymaking and informing public narrative are characterized by scientific reticence, paying limited attention to lower-probability, high-risk events that are becoming increasingly likely. (Disclosure: I was a co-author of this report.) 

But don’t take my word.  At the climate policy conference in Bonn, Phil Duffy, the Director of the Woods Hole Institute, explained the scientific reticence regarding the biggest system feedback issues:

"The best example of reticence is permafrost…  It’s absolutely essential that this feedback loop not get going seriously, if it does there is simply no way to control it… The scientific failure comes in because none of this is in climate models and none of this is considered in the climate policy discussion… climate models simply omit emissions from the warming permafrost, but we know that is the wrong answer because that tacitly assumes that these emissions are zero and we know that’s not right…"

And the problems of underestimation of future climate impacts from current models was explicitly recognized by the US government in its Climate Science Special Report: Fourth National Climate Assessment. In a chapter on “Potential Surprises: Compound Extremes and Tipping Element,” two key findings were:

Positive feedbacks (self-reinforcing cycles) within the climate system have the potential to accelerate human-induced climate change and even shift the Earth’s climate system, in part or in whole, into new states that are very different from those experienced in the recent past (for example, ones with greatly diminished ice sheets or different large-scale patterns of atmosphere or ocean circulation). Some feedbacks and potential state shifts can be modeled and quantified; others can be modeled or identified but not quantified; and some are probably still unknown. (Very high confidence in the potential for state shifts and in the incompleteness of knowledge about feedbacks and potential state shifts).

• While climate models incorporate important climate processes that can be well quantified, they do not include all of the processes that can contribute to feedbacks, compound extreme events, and abrupt and/or irreversible changes. For this reason, future changes outside the range projected by climate models cannot be ruled out (very high confidence). Moreover, the systematic tendency of climate models to underestimate temperature change during warm paleoclimates suggests that climate models are more likely to underestimate than to overestimate the amount of long-term future change (medium confidence).

• The problem is that the notion that future climate changes may be faster and hotter than those projected by climate models is one rarely understood by climate policy-makers, and rarely discussed by those who do understand.

If climate policymaking is to be soundly based, a re-framing of scientific research within an existential risk-management framework is now urgently required. This must be taken up not just in the work of the IPCC, but also in the UN Framework Convention on Climate Change negotiations if we are to address the real climate challenge.

http://www.climatecodered.org/2018/01/what-we-learned-about-climate-system-in.html

2017’s costly climate change-fueled disasters are the ‘new normal,’ warns major reinsurer Munich Re

“We have a new normal” thanks to climate change, explains leading reinsurer.

by Joe Romm, Climate Progress, January 4, 2018

HURRICANE HARVEY IMPACTS. CREDIT: GETTY IMAGES

It turns out 2017 was a uniquely disastrous year in more ways than one, evidenced by German reinsurer Munich Re’s recently released review of the year’s global catastrophes.

Led by massive, climate change-fueled hurricanes Harvey, Irma, and Maria, 2017’s natural disasters will cost insurers a record $135 billion. Adding in uninsured losses brings the total global damages to $330 billion, which is second only to 2011.

“We have a new normal,” Munich Re’s Ernst Rauch told Reuters. Rauch, who runs the group tracking climate change risks, pointed out that “2017 was not an outlier” in having more than $100 billion in insured losses (see chart below). “We must have on our radar the trend of new magnitudes,” Rauch said.

The big reinsurers like Munich Re make their money by insuring the companies that directly insure your property. Those smaller companies are often required by law to buy reinsurance because they lack the capital resources to pay out if there is a major disaster, like superstorm Harvey for instance.

Since the reinsurers must pay out billions and billions of dollars for such mega-disasters, they have a unique incentive to understand and predict trends in mega-disasters. That’s why companies like Munich Re and Swiss Re have been at the forefront of warning businesses and the public about the rise in extreme weather events due to climate change.

Indeed, back in September 2010, another year of stunning warming-driven extreme weather events, Munich Re issued a release noting it had analyzed its catastrophe database, “the most comprehensive of its kind in the world,” and concluded, “the only plausible explanation for the rise in weather-related catastrophes is climate change.” 

Then in October 2012, the company released a massive 274-page report, “Severe weather in North America,” analyzing weather catastrophes and related losses since 1980 to understand trends and their causes, including man-made climate change.

Munich Re found that the number of weather-related loss disasters has been rising much faster in North America than anywhere else, and concluded, “Climate-driven changes are already evident over the last few decades for severe thunderstorms, for heavy precipitation and flash flooding, for hurricane activity, and for heatwave, drought and wild­fire dynamics in parts of North America.”

Prof. Peter Höppe, who heads Munich Re’s Geo Risks Research unit, said at the time, “In all likelihood, we have to regard this finding as an initial climate-change footprint in our U.S. loss data from the last four decades.”

And last April, Munich Re published an article on “rapid attribution,” which explained that we can now rapidly determine how much intensity or frequency of some extreme weather events is affected by man-made climate change. Learning that, for instance, climate change has sharply increased the chances of individual extreme rain and flooding events – such as devastating August 2016 deluge and flooding of Baton Rouge, Louisiana – allows communities to do better planning and Munich Re to do better risk management.

The latest annual report amplifies the message that humans are changing the climate, boosting the intensity and frequency of extreme weather events, and that the longer we dawdle, the higher the costs we will incur. The only question is, is anyone listening?

https://thinkprogress.org/weather-disaster-record-cost-4948070d8e53/

Northern Hemisphere jet streams stumble as the world warms

The warming of the atmosphere by greenhouse gases is slowing the jet streams which drive the Northern Hemisphere's weather, scientists say. 

by Tim Radford, Climate News Network, April 9, 2017

LONDON – Researchers have once again linked a sequence of devastating climate events to global warming fuelled by prodigal human use of fossil fuels. And this time, they believe they have identified the agency behind the blazing summers that have claimed lives and destroyed livelihoods repeatedly during this century.

They argue in the journal Scientific Reports that human impact on the climate now reaches high into the stratosphere, to influence the behaviour patterns of the giant jet streams that carry heat and moisture around the Northern Hemisphere and keep the weather on the move.

Warming driven by carbon dioxide emissions from car exhausts and power stations, they argue, tends to make these giant oscillating waves stall in their journey around the hemisphere – to create enduring episodes of high and low pressure and lingering hazards of drought and flood.

“The unprecedented 2016 California drought, the 2011 US heatwave and 2010 Pakistan flood as well as the 2003 European hot spell all belong to a most worrying series of extremes,” says Michael Mann from Pennsylvania State University in the US.

“Human activity has been suspected of contributing to this pattern before, but now we uncover a clear fingerprint of human activity”

“The increased incidence of these events exceeds what we would expect from the direct effects of global warming alone, so there must be an additional climate change effect. In data from computer simulations as well as observations, we identify changes that favour unusually persistent, extreme meanders of the jet stream that support such extreme weather events.

“Human activity has been suspected of contributing to this pattern before, but now we uncover a clear fingerprint of human activity.”

Professor Mann has repeatedly confirmed the link between human action and climate change. His co-author Dim Coumou of the Potsdam Institute for Climate Impact Research in Germany and the VU University in Amsterdam in the Netherlands has separately linked storm tracks to surface temperature extremes, made a connection between torrential rains and planetary warming, and confirmed too that less stormy weather is not necessarily a good sign, because it could be the harbinger of heat waves.

And the researchers now have support for their their suspicions: the jet streams that sweep the hemisphere in huge atmospheric waves, plunging between Arctic and tropics, bring changes of weather.

If they should stall, one region may be committed to long drought, dangerous hot weather (as in Russia in 2010 and Texas in 2011) and even forest fires as in California in 2015) – or, in some cases, catastrophic and sustained rainfall of the kind that flooded Pakistan in 2010.

Questions remain

No single extreme event could ever be satisfactorily and conclusively linked to a long-term trend like global warming. But once scientists register an increasing frequency of such events, they can start to use climate simulations to see if such events become more likely in a warming world.

“The more frequent persistent and meandering jet stream state seems to be a relatively recent phenomenon, which makes it even more relevant," said Dr Coumou. “We certainly need to further investigate this – there is some good evidence, but also many open questions.”

And Professor Mann said: “The warming of the Arctic, the polar amplification of warming, plays a key role here. The surface and lower atmosphere are warming more in the Arctic than anywhere else on the globe.

“That pattern projects onto the very temperature gradient profile that we identify as supporting atmospheric waveguide conditions.”

http://climatenewsnetwork.net/jet-streams-stumble-as-world-warms/

Global warming's fingerprints are all over recent extreme weather, research shows

IMAGE: DANIEL KALISZ/GETTY IMAGES

by Andrew Freedman, Mashable, November 5, 2015

Extreme weather events, from droughts to floods and heat waves, are some of the most tangible present day impacts of global warming, and they will take center stage in speeches at the upcoming Paris Climate Summit. Now a new report gives leaders pushing to reduce emissions of global warming pollution, including President Obama, additional ammunition.

The report, published Thursday as a special supplement to the Bulletin of the American Meteorological Society, amounts to the largest-ever assessment of global warming’s role in intensifying the severity and altering the likelihood of extreme weather events during 2014.

It amounts to the equivalent of a climate change CSI report, and its conclusions are damning in pointing to global warming as being an accomplice to numerous damaging extreme events worldwide.

In total, the report contains analyses from 32 different research groups examining 28 extreme weather and climate events on all continents. The dozens of researchers from 21 countries found that climate change’s fingerprints are all over the scene of the crime in more than half of these events, including California wildfires, Middle Eastern drought and heat waves in Australia.

Specifically, tropical cyclones in the central Pacific, deadly heat waves in Australia, Asia and South America, and a deadly snowstorm in the Himalayas, were each in part the result of human activities, the studies show.

“For each of the past four years, this report has demonstrated that individual events, like temperature extremes, have often been shown to be linked to additional atmospheric greenhouse gases caused by human activities, while other extremes, such as those that are precipitation related, are less likely to be convincingly linked to human activities,” said Tom Karl, director of the National Centers for Environmental Information in Asheville, North Carolina.

“As the science of event attribution continues to advance, so too will our ability to detect and distinguish the effects of long-term climate change and natural variability on individual extreme events. Until this is fully realized, communities would be well-served to look beyond the range of past extreme events to guide future resiliency efforts."

These studies are part of a new and increasingly sophisticated subfield within climate science known as extreme event attribution, which involves attempts to tease out the influence of climate change, natural variability and other factors that go into extreme events.

Notably, each of the assessments of extreme climate events in Australia found clear evidence of human influences, including increased likelihood of a heat wave in Brisbane, Australia, heat waves in Adelaide and Melbourne in January 2014, record warm spring temperatures across Australia.

Man-made extremes

The events that had a man-made component to them included tropical cyclones that hit Hawaii, the Argentinean heat wave of 2013, and Australian heat waves.

Four separate studies by different scientific teams found that human influences, mainly in the form of increased emissions of global warming pollutants, caused a substantial increase in the likelihood and severity of several heat waves that struck Australia in 2014. These included events in Melbourne and in Brisbane, where extreme heat hit during the G20 Summit and global warming was conspicuously absent from leaders’ agenda.

For example, climate model simulations for 2014 indicated that man-made global warming “very likely increased the likelihood of hot and very hot November days in Brisbane by at least 25% and 44% respectively,” the G20 heat wave study concluded.

Another study published Thursday found that the record warm Australian spring of 2014, during which all-time temperature records were exceeded across the continent, “would likely not have occurred without increases in carbon dioxide over the last 50 years,” combined with weather patterns in the upper atmosphere.

Perhaps the most fascinating, albeit extremely deadly, event scientists analyzed was the blizzard that killed 43 people, including 21 trekkers, in the Himalayas. This storm resulted from the combination of Category 4 Tropical Cyclone Hudhud with other weather systems in a rare confluence of extreme events.

The study found that climate change increases the odds of such “unusual mergers” between tropical cyclones and upper level weather disturbances, because of the ways it is changing weather patterns in that region. The study detected a northward shift in intense tropical cyclones in the Bay of Bengal, as well as an intensification in the strongest storms that have occurred as water temperatures in the area have increased.

These changes have raised the risk of such storms in northeastern India and increased the frequency of extremely high amounts of moisture slamming up against the wall of the Himalayan Mountains in Nepal, where such water vapor falls as heavy snow.

“The implication of these results is that, although weather systems similar to that of 13–14 October 2014 did occur in the past, there is a tendency for both types of weather systems to interact more frequently,” the study said.

The Nepal disaster, which was the deadliest event in the history of Nepal’s mountain climbing history, had some similarities to Hurricane Sandy, when a massive tropical cyclone in the Western Atlantic interacted with a feature in the jet stream to bring several feet of snow to West Virginia while flooding parts of the East Coast with a deadly storm surge.

In addition, another study using computer modeling found that man-made global warming has increased the odds of unusually high sea surface temperatures in the western tropical Pacific Ocean and northeast Pacific Ocean. Such temperature extremes contributed to record heat in Alaska and whole scale shifts in the distribution of sea life, as well as changes in tropical cyclone behavior in the western tropical Pacific.

Many studies turned up little evidence of a man-made influence

Many studies did not turn up a man-made influence on particular extreme events, although every weather event today takes place in an atmosphere altered by man-made activities.

One study by scientists at Spain’s Barcelona Supercomputing Center, found that the all-time maximum in Antarctic sea ice in 2014 was mainly the result of unusual wind patterns that enhanced offshore production of sea ice. The study found that these winds, and the resulting spike in sea ice extent, are now less likely to occur due to climate change.

All-time maximum of Antarctic sea ice in 2014 resulted chiefly from anomalous winds that transported cold air masses away from the Antarctic continent, enhancing thermodynamic sea ice production far offshore. This type of event is becoming less likely because of climate change.

The authors of the overall report noted that attribution assessments are limited by the often limited observational records and limitations of computer models. “In general, when attribution assessments fail to find anthropogenic [man-made] signals this alone does not prove anthropogenic climate change did not influence the event,” the report states. “The failure to find a human fingerprint could be due to insufficient data or poor models and not the absence of anthropogenic effects.”

Looking back a year later: what’s the relevance to society?

The examination of 2014’s extremes demonstrates a major weakness of these studies so far, which is that they frequently take so long to be completed that they come months or a year or more after the events themselves. This is well after such events have disappeared from the news, and after many of the governmental leaders who dealt with these events — such as former Australian Prime Minister Tony Abbott — have left office.

Such studies often require supercomputing resources obtained either through national supercomputing centers — such as at Barcelona or the National Center for Atmospheric Research in Colorado — or distributed computing, in which everyday citizens use their home computers’ down time to perform computations for climate scientists. This project, known as Weather At Home, is led by a team in the U.K. and partially funded by The Guardian newspaper and Microsoft.

“Understanding our influence on specific extreme weather events is groundbreaking science that will help us adapt to climate change,” said Stephanie Herring, lead editor for the report.

“As the field of climate attribution science grows, resource managers, the insurance industry, and many others can use the information more effectively for improved decision making and to help communities better prepare for future extreme events.”

There are ongoing efforts to change this, however, and make more rapid assessments.

http://mashable.com/2015/11/05/extreme-weather-global-warming/