New Climate Risk Classification Created to Account for Potential “Existential” Threats

Researchers projected warming scenarios that vary based on what societal actions are taken to reduce emissions. Graphic credit: Scripps Institution of Oceanography.

From the Scripps Institution of Oceanography (Robert Monroe):

A new study evaluating models of future climate scenarios has led to the creation of the new risk categories “catastrophic” and “unknown” to characterize the range of threats posed by rapid global warming. Researchers propose that unknown risks imply existential threats to the survival of humanity.

These categories describe two low-probability but statistically significant scenarios that could play out by century’s end, in a new study by Veerabhadran Ramanathan, a distinguished professor of climate and atmospheric sciences at Scripps Institution of Oceanography at the University of California San Diego, and his former Scripps graduate student Yangyang Xu, now an assistant professor at Texas A&M University.

The risk assessment stems from the objective stated in the 2015 Paris Agreement regarding climate change that society keep average global temperatures “well below” a 2°C (3.6°F) increase from what they were before the Industrial Revolution.

Even if that objective is met, a global temperature increase of 1.5°C (2.7°F) is still categorized as “dangerous,” meaning it could create substantial damage to human and natural systems. A temperature increase greater than 3°C (5.4°F) could lead to what the researchers term “catastrophic” effects, and an increase greater than 5°C (9°F) could lead to “unknown” consequences which they describe as beyond catastrophic including potentially existential threats. The specter of existential threats is raised to reflect the grave risks to human health and species extinction from warming beyond 5°C, which has not been experienced for at least the past 20 million years.

The scientists term warming probability of five percent or less as a “low-probability high-impact” scenario and assess such scenarios in the analysis “Well Below 2°C: Mitigation strategies for avoiding dangerous to catastrophic climate changes,” which appears today in the journal Proceedings of the National Academy of Sciences.

Ramanathan and Xu also describe three strategies for preventing the gravest threats from taking place.

“When we say 5 percent-probability high-impact event, people may dismiss it as small but it is equivalent to a one-in-20 chance the plane you are about to board will crash,” said Ramanathan. “We would never get on that plane with a one-in-20 chance of it coming down but we are willing to send our children and grandchildren on that plane.”

The researchers defined the risk categories based on guidelines established by the Intergovernmental Panel on Climate Change (IPCC) and previous independent studies. “Dangerous” global warming includes consequences such as increased risk of extreme weather and climate events ranging from more intense heat waves, hurricanes, and floods, to prolonged droughts. Planetary warming between 3°C and 5°C could trigger what scientists term “tipping points” such as the collapse of the West Antarctic Ice Sheet and subsequent global sea-level rise, and the dieback of the Amazon rainforest. In human systems, catastrophic climate change is marked by deadly heat waves becoming commonplace, exposing over 7 billion people to heat related mortalities and famine becoming widespread. Furthermore, the changes will be too rapid for most to adapt to, particularly the less affluent, said Ramanathan.

Risk assessments of global temperature rise greater than 5°C have not been undertaken by the IPCC. Ramanathan and Xu named this category “unknown??” with the question marks acknowledging the “subjective nature of our deduction.” The existential threats could include species extinctions and major threats to human water and food supplies in addition to the health risks posed by exposing over 7 billion people worldwide to deadly heat.

With these scenarios in mind, the researchers identified what measures can be taken to slow the rate of global warming to avoid the worst consequences, particularly the low-probability high-impact events. Aggressive measures to curtail the use of fossil fuels and emissions of so-called short-lived climate pollutants such as soot, methane and HFCs would need to be accompanied by active efforts to extract CO2 from the air and sequester it before it can be emitted. It would take all three efforts to meet the Paris Agreement goal to which countries agreed at a landmark United Nations climate conference in Nov 2015.

“This report shines a bright light on the existential threat that climate change presents to all humanity,” said Calif. Governor Edmund G. Brown Jr., who has collaborated with Ramanathan on carbon neutrality measures in the state. “Scientists have many ideas about how to reduce emissions, but they all agree on the urgency of strong and decisive action to remove carbon from the economy.”

Xu and Ramanathan point out that the goal is attainable. Global CO2 emissions had grown at a rate of 2.9 percent per year between 2000 and 2011, but had slowed to a near-zero growth rate by 2015. They credited drops in CO2 emissions from the United States and China as the primary drivers of the trend. Increases in production of renewable energy, especially wind and solar power, have also bent the curve of emissions trends downward. Other studies have estimated that there was by 2015 enough renewable energy capacity to meet nearly 24 percent of global electricity demand.

Short-lived climate pollutants are so called because even though they warm the planet more efficiently than carbon dioxide, they only remain in the atmosphere for a period of weeks to roughly a decade whereas carbon dioxide molecules remain in the atmosphere for a century or more. The authors also note that most of the technologies needed to drastically curb emissions of short-lived climate pollutants already exist and are in use in much of the developed world. They range from cleaner diesel engines to methane-capture infrastructure.

“While these are encouraging signs, aggressive policies will still be required to achieve carbon neutrality and climate stability,” the authors wrote.

The release of the study coincides with the start of Climate Week NYC in New York, a summit of business and government leaders to highlight global climate action. Ramanathan and colleagues will deliver a complementary report detailing the “three-lever” mitigation strategy of emissions control and carbon sequestration on Sept. 18 at the United Nations. That report was produced by the Committee to Prevent Extreme Climate Change, chaired by Ramanathan, Nobel Prize winner Mario Molina of UC San Diego, and Durwood Zaelke, who leads an advocacy organization, the Institute for Governance and Sustainable Development, with 30 experts from around the world including China and India.

#ColoradoRiver District seminar recap @ColoradoWater #CRDseminar #COriver

Rebecca Mitchell was named to the Colorado Water Conservation Board on July 5, 2017. Photo credit the Colorado Independent.

From The Grand Junction Daily Sentinel (Dennis Webb):

Becky Mitchell, who has been the director of the Colorado Water Conservation Board for about two months, spoke Friday at the Colorado River District’s annual water seminar in Grand Junction.

She told attendees that when it comes to meeting the state’s water needs, “it’s really all hands on deck. Everyone here plays an important role. … What you’re doing is equally as important as anything we’re doing.”

Steps already taken by entities ranging from her agency to the river district to agricultural interests, environmental stakeholders and members of river basin roundtables “have really shown me that we are at a point where we’re ready to work together and that the success that we’ve had has been because of collaboration,” Mitchell said.

In comments to the group and in an interview, she addressed the monetary challenges for Colorado in meeting its future water needs. An initial estimate for paying for projects identified in the new water plan in coming decades was about $20 billion — already a daunting amount — but Mitchell’s agency now believes the price tag could be twice that much when the cost of water quality projects, generally involving water or wastewater treatment, are included.

The state water board is looking into the cost issue through a statewide water supply initiative analysis that is expected to come out next year…

She said it will be important to rely on a prioritization of projects by roundtable groups in each river basin. Also key is to focus on projects that provide multiple benefits, because having multiple interests in a project could lead to multiple sources of money to pay for it, she said.

“It’s not necessarily the responsibility of the state to come up with the entire amount to implement the water plan,” Mitchell said. “A lot of it goes back to the local level and how we can support work that’s being done on the ground.”

Mitchell worked on developing the plan as a staff member of her agency before being promoted after her predecessor, James Eklund, left to take a job as an attorney with a legal firm.

“We’re at a really important time in the state where we have a capability to make a big difference in how we’re looking at our water future. It’s an exciting time and I’m excited to be a part of it,” Mitchell said.

As for Eastern Slope/Western Slope water matters, “I am optimistic that we’ll be able to work through issues like we have done. When we’ve found solutions, it’s when we’ve come together regardless of the side of the (Continental) Divide. I think where we’re going to see solutions is where we come together,” she said.

Eric Kuhn along the banks of the Colorado River in Glenwood Springs, general manager of the Colorado River District. Photo via the Grand Junction Daily Sentinel.

From KJCT8.com:

The Colorado River is the hardest working river in the world, that’s according to local experts. Hundreds of water experts are gathered in the valley to put together their game plan to tackle the biggest challenges facing the river.

The General Manager Colorado River Water Conservation District, Erik Kuhn, says there are a lot of ideas to better manage the Colorado River, before it runs out in southern California. In order to stretch the water even further, one idea is to move the waters in Lake Powell to Lake Mead.

“So it would allow for the recovery of lands that are now inundated by water in Lake Powell, natural recovery of those. It’s called the ‘Fill Mead First’. He’s talking about that. We don’t think that works very well for a number of reasons. But it’s one of those things that’s caught a lot of press attention of late,” Kuhn said.

The Colorado River helps supply water to people in Denver all the way to about 20 million people in the Los Angeles, California area.

The Colorado River Basin is divided into upper and lower portions. It provides water to the Colorado River, a water source that serves 40 million people over seven states in the southwestern United States. Colorado River Commission of Nevada