Here’s an in-depth report from Laura Paskus that’s running in The Santa Fe Reporter. Click through and read the whole article. Here’s an excerpt:
Today, we know the [firefighting] foam contained toxic chemicals responsible for polluting the water around hundreds of military bases nationwide, including Cannon and Holloman Air Force bases in New Mexico. And the toxic chemicals are present in the drinking water of millions of Americans…
Over the years, [Kevin] Ferrara has learned that the military knew Aqueous Film Forming Foam (AFFF) was dangerous—and so did the companies that manufactured it. But without federal regulations that set drinking water standards or hazardous waste limits, states like New Mexico still can’t hold the Pentagon accountable for the pollution that has crept from the bases into the wells of local residents and businesses. Meanwhile, military firefighters like Ferrara wonder what’s happening within their own bodies—and the bodies of those whose water they polluted.
In the waning days of Gov. Susana Martinez’s administration, the New Mexico Environment Department (NMED) was grappling with a problem. A “forever” problem, as it turns out.
Contractors hired by the military were investigating whether AFFF used at the state’s three Air Force bases had contaminated groundwater with PFAS.
In an August 2018 conference call, Air Force officials told state officials that PFAS had been found in wells at Cannon Air Force Base at concentrations above the US Environmental Protection Agency’s lifetime health advisory of 70 parts per trillion. Further studies showed the levels exceed 26,000 parts per trillion—more than 370 times that EPA health advisory—and that PFAS was also in off-base wells that supply homes and dairies in Clovis.
In October, NMED, the New Mexico Department of Health and the New Mexico Department of Agriculture publicly announced the presence of the contamination on and off the base. They advised private well-owners within a 4-mile radius of the base to use bottled water. NMED issued a notice of violation against the Air Force for breaking state regulations. The agency issued “corrective action permits” with cleanup mandates for the military’s state permits.
But in January 2019, just after Gov. Michelle Lujan Grisham took office, the US Department of Defense sued New Mexico, challenging the state’s authority to mandate cleanup.
And although the state made no announcements nor issued any corrective actions, a report the Air Force submitted to NMED during the Martinez administration showed that groundwater samples of PFAS at Holloman Air Force Base were as high as 1.294 million parts per trillion. In February 2019, NMED issued a notice of violation against the Air Force over Holloman, too.
The following month, in March 2019, New Mexico filed its own lawsuit, asking a federal judge to compel the Air Force to act on, and pay for, cleanup at Cannon and Holloman.
But that hasn’t worked out as planned.
“We wanted action quickly. When that wasn’t available, or that wasn’t on the table, that’s when we litigated,” NMED Secretary James Kenney says in an interview.
The lawsuit has been lumped in with hundreds of other PFAS-related lawsuits. One court in South Carolina now oversees all cases regarding PFAS and the military’s use of the AFFF—more than 750 separate actions.
Even though New Mexico has tried to extricate itself from the multidistrict litigation, hoping to pursue its case against the Air Force without being tied to those hundreds of other cases, a judge has denied that request. And in June, the Biden administration’s Defense Department called New Mexico’s attempts to compel cleanup under state permits “arbitrary and capricious.”
In summary, three years after the Air Force notified New Mexico of the PFAS pollution, there are no clean-up plans in place at Cannon or Holloman, though earlier this year, Cannon announced an on-base pilot project to test the best ways to remove PFAS from water. And even though the military knows when, why and how the contamination happened, it has sued New Mexico to say the state can’t make it clean up the problem.
Meanwhile, state Environment Sec. Kenney says the EPA needs to set federal pollution standards for the toxic substances.
In 2016, the EPA established a lifetime health advisory for two types of PFAS found in firefighting foams, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). But that advisory of 70 parts per trillion isn’t a regulatory limit. That means states like New Mexico don’t have any legal tools to require that polluters like the military clean up PFAS.
John Rauch and his family have operated the Cedar Springs Marina here since 1986. But three weeks ago, when the federal government suddenly ordered millions of gallons of water to be released from Flaming Gorge Reservoir down the Green River to Lake Powell, Rauch wasn’t prepared.
“It was a total gut punch,” he said on a recent hot, sunny morning. As visitors trekked down to rent his pontoon boats, and others slid their fishing craft into the reservoir, Rauch and his employees were already planning which boat docks and ramps would have to be relocated to keep them afloat. The reservoir is projected to drop as much as 2 feet a month through the fall as water is released.
Drought has plagued the Colorado River Basin for 20 years, but it hit crisis proportions this summer, pushing lakes Powell and Mead to historic lows and triggering, for the first time, emergency releases of water from Utah’s Flaming Gorge, Colorado’s Blue Mesa, and New Mexico’s Navajo reservoirs.
All told, 181,000 acre-feet of water are to be sent to Lake Powell by the end of December. Powell has dropped so low that its hydropower plants, which supply millions of homes with electricity and generate revenue for such things as a critical Colorado River endangered species program, may stop operating as early as next year if water levels continue to drop as they have been. The U.S. Bureau of Reclamation estimates there is a 3 percent chance of this occurring next year and a 29 percent chance of this occurring in 2022. But given the speed of the Powell’s decline, no one wants to risk a hydropower shutdown.
Since their construction in the 1960s these reservoirs, known as Reclamation’s Colorado River Storage Project reservoirs, have acted as a giant savings account, helping ensure that if a crisis erupted on the river, the Upper Colorado River Basin states of Colorado, Wyoming, Utah and New Mexico would have enough water on hand to fulfill their legal obligation to deliver water to Nevada, Arizona and California, known as the Lower Basin states.
Colorado’s Blue Mesa Reservoir, part of the Aspinall Unit, is already low, at just 43 percent of capacity as of last month. Fed by the Gunnison River, a major tributary of the Colorado, the reservoir is tourism hot spot on Colorado’s West Slope.
Kathleen Curry, a former Colorado lawmaker, sits on the Colorado River District Board. She said she understands the need for the releases, but she said the changes in the shoreline at Blue Mesa aren’t going unnoticed.
“It’s taking residents and visitors by surprise, just because I don’t think anyone was expecting it,” she said.
The releases come under a special Upper Basin Drought Contingency Plan approved by Colorado, Wyoming, Utah and New Mexico in late 2018. A similar drought plan is in place for the Lower Basin, and they have been cutting back withdrawals from Lake Mead for the past two years.
Still the river system is drying out. And water leaders in Colorado are deeply worried that their carefully protected savings account is going to dry up too quickly to solve the Colorado River’s long-term problems.
Will it work?
“I understand and support the necessity of the Secretary [of the Interior] taking this action,” said Jim Lochhead, CEO of Denver Water. “The major concern I have is that Reclamation says the 181,000 acre-foot release will raise Lake Powell three feet. But I don’t know that they can even show that. I don’t know that they have accounted for transit losses and other losses.
“It’s important when these releases are made that they are accounted for, that we know where this water is going. If it doesn’t actually get down to [Lake Powell] to accomplish what it was designed to do, we should have kept it in that savings account,” Lochhead said.
Becki Bryant, a spokesperson for the U.S. Bureau of Reclamation’s Upper Colorado River region, said the agency is working to create a hydropower buffer in Lake Powell and believes the releases are adequate to accomplish that. But Reclamation is not yet doing the kind of precise tracking and accounting known as water “shepherding,” to ensure flows make it downstream, that Lochhead is requesting.
On Aug. 1, Lake Powell’s elevation stood at 3,553.8 feet above sea level. The action point, or so-called target elevation is 3,525. When that point came close in July, Reclamation moved quickly to order the emergency releases.
Powell’s hydropower plant stops generating power when it drops to 3,490 feet in elevation, according to Reclamation.
“Reclamation expects the additional release of water will be sufficient to protect Lake Powell’s target elevation through 2021. That target elevation provides a 35-vertical-foot buffer designed to minimize the risk of dropping below the minimum power pool elevation of 3,490 feet, and balances the need to protect the infrastructure at Powell’s Glen Canyon Dam.
“Shepherding water would be beneficial but is challenging on many levels for Colorado River Basin states,” said Bryant via email.
Bryant said Reclamation will continue to consult with the Upper Basin states as it monitors reservoir levels and weather forecasts. Should conditions deteriorate further, the agency could examine whether to declare the releases futile and stop them, as it is allowed to do under the 2018 Drought Contingency Plan.
The water being released is so-called “system water,” meaning that it isn’t owned by a particular user.
Held by the federal government for the benefit of the Upper Basin states, the amounts of water specified in the release plan are jaw-dropping: 125,000 acre-feet from Flaming Gorge; 36,000 acre-feet from Blue Mesa; and 20,000 acre-feet from Navajo. An acre-foot of water is enough to cover one acre of land to a depth of 12 inches.
If that same amount of water were going to cities, it would be enough to serve more than 362,000 homes for one to two years. If going to farms, it could irrigate more than 113,000 acres, depending on the crop.
If the historic, 20-plus-year drought cycle doesn’t end soon, refilling those reservoirs is going to be difficult. And that has water managers worried.
“My level of concern is quite high,” said Becky Mitchell, director of the Colorado Water Conservation Board, the state’s lead water planning and policy agency. She also sits on the four-state Upper Colorado River Basin Commission, which advises Reclamation on river issues.
“And I can’t tell yet if [the releases] are going to do the trick,” she said. “But we have to respond to the levels in Powell.”
Under the 1922 Colorado River Compact, Colorado and the other Upper Basin states must deliver 7.5 million acre-feet (maf) [per year, 75 maf per 10 years] of water to the Lower Basin on a 10-year running average. Right now, the Upper Basin is delivering roughly 9.2 maf, Mitchell said, meaning that there is still time to help the system come back into balance before the Lower Basin states could legally call for more water than they currently receive.
Lake Powell is the Upper Basin’s largest storage pool on the system and is designed to be the four Upper Basin states’ major source of protection. Because of their legal obligations, Colorado water users are closely monitoring this year’s plunge in Powell, with the threat to hydropower production being seen as a dangerous antecedent to a compact call.
“That the system continues to deteriorate is concerning,” Lochhead said.
Roughly half of Denver Water’s supplies are derived from water rights it owns on the Colorado River system. While one portion of its portfolio dates back to 1921, and would therefore trump a 1922 compact call, several other rights were established later, meaning the utility might have to stop pulling from those water sources if Colorado were forced to cut back in order to meet compact obligations.
Other Front Range water providers, who also have Colorado River rights, are even more vulnerable, including the Pueblo-based Southeastern Colorado Water Conservancy District.
Southeastern’s rights date only to 1957.
Contingency v. reality
Lee Miller, Southeastern’s attorney, said the Colorado River crisis remains a long-term problem for his agency.
The rapid deterioration this year, however, is prompting everyone to rethink how much time they have to balance the massive river system as drought and a warming climate, as well as population growth, continue to sap its flows.
“Both the Upper and Lower Basin have now had to initiate elements of their drought contingency plans. When we passed it a couple of years ago everyone thought, “It’s good to have a contingency plan.’ But I don’t think anyone thought we would have to use the plans this quickly. It’s gone from being a contingency to being a reality, and that’s concerning.”
Back up at Flaming Gorge, John Rauch is watching the levels drop and making his own contingency plans.
“We are planning for the worst,” Rauch said. “For the foreseeable future, the outlook is dry. If it ends up that by the end of all of this that the reservoir becomes a river channel, we will be down there at water’s edge selling worms.”
Jerd Smith is editor of Fresh Water News. She can be reached at 720-398-6474, via email at firstname.lastname@example.org or @jerd_smith.
The Snake River Water District will undergo a variety of rehabilitation and improvements throughout the next 10 years based on its 2021 master plan.
The district, which provides drinking water to the Keystone valley, underwent a study with an engineering firm to look at its infrastructure’s strengths and weaknesses. The idea to look into infrastructure upgrades started about two years ago when the district was notified it had a slight lead exceedance based on two water samples.
Scott Price, executive director and district administrator, said this occurs not because there is an issue with the actual water, but because pipes in some older homes in the area were built with lead and are still in use. If the water sits in the pipes for too long, it can lead to concentrations of lead in the water samples. Price said the Colorado Department of Public Health and Environment has to use the water that first comes out when the faucet is turned on when it tests water samples, which will likely be affected by lead if the water sat unused in old pipes.
The district has three base plants, each with its own storage and water filtration system. The second base, which is also home to the district’s office, is likely to need an additional storage tank to serve the high-density area of Keystone Resort, as well as a pump station that can transport water uphill from the third to the second base.
An existing infrastructure issue to address is water pipe breakage, something Price said can cost around 10 times more to fix in the winter than it does in the summer. Engineers looked at which pipes were more likely to break, but also the severity of consequences that can occur from a breakage.
The study prioritized which pipes and fire hydrants in the district would need attention immediately, creating a map showing the different priorities based on each area. The district plans to chip away at these pipe and hydrant upgrades little by little during the 10-year plan.
Meanwhile, the third plant underwent $8.5 million in upgrades a couple years ago, including a new filtration system. Price said he expects this filtration system to be in compliance for decades to come as water quality regulations get tighter over time…
Price also said that should the base two plant need upgrades — which he is expecting to get a decision from the Colorado Department of Public Health and Environment by the end of the year — the whole district will be able to temporarily operate on the new base three plant.
Lastly, the study showed that the district’s Pilot Lode storage tank by the Settlers Creek townhomes will need improvements to its interior lining, as it is around 25 years old and steel constructed.
The study estimates that over 10 years, the district will need about $38.5 million in work, estimated as follows:
Pump station from base three to base two: $1.5 million
Base two storage tank: $7.6 million
Base two groundwater under direct influence compliance: $11.8 million
Pilot Lode tank rehabilitation: $550,000
Pipeline replacements: $13.5 million
Fire hydrant replacements: $1.6 million
On top of these costs there are several smaller projects included in the master plan that account for the remaining $2 million of the budget. These estimates cover only the cost of construction, and the district will need to pay more in the coming months for architects and engineers to design the systems…
The plan calls for a 12% rate increase at the start of 2022, and the Snake River Water District’s board is currently planning to do 12% increases over the next three years. The base quarterly fee will go from $65 in 2022 to $91 in 2024.
The Snake River Water District hasn’t increased its water rates in about eight years, which was then only a 3% increase. Prior to that, it hadn’t raised its quarterly rates since the 1990s.
A group of Colorado residents demonstrated Saturday against the construction of a reservoir in the Homestake Valley, marching through the streets of Red Cliff and treating passing vehicles to a variety of colorful signs.
If you were headed south on Highway 24 on Saturday afternoon, you might have been able to read a clever statement like “Stop the whole dam thing,” and “They can’t ‘fen’ for themselves.”
Or you might have noticed a message or two that was more direct. Using an elongated trash picking tool to hoist her sign, Silverthorne resident Jan Goodwin wrote “CO Springs doesn’t need Red Cliff’s water.”
The group is opposed to building a new reservoir in the Homestake Valley 6 miles southeast of Red Cliff, which would be used by the people of Colorado Springs and Aurora, who hold water rights in the area, including the rights to the water in the existing Homestake Reservoir.
But the nuances of the issue, including the sensitive wetlands known as “fens” and the study required for “the whole dam thing,” as referenced in the signs, was also discussed among the demonstrators. In order to construct a new dam and reservoir, the area will require some study, and the Forest Service has already approved that study, which will allow the cities to drill “10 bore samples up to 150-feet deep using a small, rubber-tracked drill rig as well as collect geophysical data using crews on foot,” according to the Forest Service, along with the construction of more than a half-mile of temporary roads to facilitate the work.
The effort could also impact up to 180 acres of wetlands on lower Homestake Creek, wetlands that include fens — groundwater-fed wetlands which began forming during the last ice age. A scientifically unproven idea to relocate the fens is being spearheaded and paid for by Aurora Water and the Board of Water Works of Pueblo…
[Charles] Fleming said he would like to see the people of Colorado Springs and Aurora make more of a good faith effort toward water conservation before seeking another reservoir in the Homestake Valley.
“I’d like to see them get rid of the green grass and focus more on xeriscaping first,” he said.
Parks said as a hotelier in Red Cliff, she sees the recreational appeal of the Homestake Valley as a wild space, not a space that would benefit from the creation of a National Recreation Area or reservoir.
One version of the reservoir envisions an encroachment into 500 acres of the Holy Cross Wilderness area of the White River National Forest, which would require an act of Congress.
A new IPCC science assessment, coming before COP26 in November, called for immediate action and showed that this summer’s extremes are only a mild preview of the decades ahead.
Amidst a summer of fires, floods and heat waves, scientists on Monday delivered yet another reminder that burning more fossil fuels in the decades ahead will rapidly intensify the impacts of global warming. Only pulling the emergency brake right now on greenhouse gas emissions can stop the planet from heating to a dangerous level by the end of the century, the scientists’ report concluded.
The report, Climate Change 2021: the Physical Science Basis, is the first installment of the Intergovernmental Panel on Climate Change’s Sixth Assessment Report (AR6), which will be completed in 2022. It was approved Aug. 6 by 195 member governments of the IPCC.
The report, by the panel’s Working Group I, assesses the physical science of climate change. It found that global warming is worsening deadly extremes like droughts and tropical storms and that every part of the planet is affected.
The report, by the panel’s Working Group I, assesses the physical science of climate change. It found that global warming is worsening deadly extremes like droughts and tropical storms and that every part of the planet is affected.
“We see this signal in all regions. No region is really spared from climate change,” said Sonia Seneviratne, a coordinating lead author of the report and a climate researcher at ETH Zürich, where she focuses on climate extremes. The report shows that “Immediate reductions of CO2 emissions would be needed to retain a chance to limit global warming close to the 2.7 degrees Fahrenheit of warming targeted by the Paris climate agreement,” she added.
Seneviratne said that it had become apparent as the scientists worked on the report that many parts of the world were vulnerable to compounded climate impacts, with “extremes of different types leading to more impacts when combined, such as the co-occurrence of heatwaves and droughts.”
Recent examples include the deadly heat wave in the Pacific Northwest that was followed by a surge of forest fires in drought-stressed, dying forests. The warmer the planet, the higher the chances of crop-killing extremes affecting different agricultural areas at the same time, she said.
The IPCC report found that, without human-caused warming, there was “a near zero probability” of some of the deadliest recent heat waves, as well as other extremes like flooding rain. “We do see we need action immediately if we want to limit warming to somewhere around 1.5 degrees Celsius,” Seneviratne added.
That global climate target, equivalent to 2.7 degrees Fahrenheit warming from pre-industrial levels, was set in 2015 as part of the Paris climate agreement, and was based on the last major climate assessment from the IPCC. The new report confirms that beyond that level of warming, parts of the climate system, like the meltdown of ice sheets that raise sea level, could spiral out of control.
IPCC vice-chairwoman Ko Barrett, a deputy administrator with the National Ocean and Atmospheric Administration, said the new report provides “unequivocal” confirmation that humans are warming the planet to a dangerous level, causing widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere in every region of the world and across the whole climate system.
It also reflects “major advances” in understanding how “climate change intensifies specific weather and climate events such as extreme heat waves and heavy rainfall events,” said IPCC Working Group I Co-Chairwoman Valérie Masson-Delmotte, a research director at the French Alternative Energies and Atomic Energy Commission.
New climate models, with more accurate data of critical climate systems like clouds, also helped make the most accurate projections to date of how the climate would respond if greenhouse gas emissions stopped. While there are still some big question marks about how much CO2 permafrost and forests will take up and release in the future, the report suggests that the climate could begin stabilizing 20 to 30 years after greenhouse gas concentrations level off.
There is also no longer any question that global warming is changing the planet’s water cycle, the report found, bringing more intense rainfalls and flooding, as well as more intense droughts in many regions. Farther north and south, in higher latitudes, precipitation is likely to increase, but expected to decline in many already dry subtropical zones.
Since 1990, the panel has released 5 major climate science assessments, about 5 to 6 years apart, with special reports focusing on specific subjects in between. Going into the global COP26 climate talks in Glasgow in November, the latest science assessment gives negotiators a robust scientific basis that can empower decision-makers to take critical action.
Steve Cornelius, a former climate negotiator with the United Kingdom government who is now the chief climate advisor for WWF, said the 2018 IPCC report, which focused on the consequences of planetary warming of more than 1.5 degrees Celsius, provided an example of how science can spur action.
“Policymakers take notice of reports from the IPCC,” Cornelius said. “We have a net zero (carbon dioxide emissions) target in the UK that came about as a direct response to the IPCC’s 2018 report. That came out, and the government asked the Committee on Climate Change to come up with a plan for net-zero.” That would not have happened without the report, he said.
But at a global level, the response to the IPCC reports has not measured up to the urgency of the situation, said Saleemul Huq, director of the International Center for Climate Change and Development in Dhaka, Bangladesh.
“Past IPCC reports have served as the basis for promises to tackle global warming,” he said “But the actions that have actually been taken in practice neither conform to what countries promised to do and are nowhere near where the science says we must be.” The new report, he said, shows “how bad things are getting and why the world needs to speed up actions in line with the scientific needs.”
Talk of Tipping Points
Stephan Singer, a senior climate advisor with Climate Action Network International who is based in Brussels, represented environmental and climate activist groups during recent IPCC meetings. ”It was refreshing to see the U.S. back in the caucus of civilized nations,” he said, as the scientists and government reviewers finalized the report.
He added that the participation by environmental groups helped ensure that the IPCC didn’t stray away from the 1.5C warming target.
“There was a fear that the 1.5 target might be dropped,” Singer said. “We wanted to make sure that it stays in there as an option. But it’s tough and challenging, and we’re losing time every day.”
Singer said the environmental groups wanted “to make sure the report makes clear the need for urgent action.”
“We need to do things now in order to have a chance to meet net-zero,” he said, “and that includes protecting and restoring natural carbon sinks, like forests. And people need to understand this is the only IPCC report coming out before COP26 and before the United Nations General Assembly so, the language must be really clear.”
“All scenarios investigated by the IPCC show that global warming will probably exceed 1.5 degrees Celsius in the next few decades,” Singer said, showing how close we are to dangerous thresholds.
“The IPCC is strongly talking about tipping points,” Singer said, “ We can’t rule out significant forest diebacks and ice sheets falling apart, or other things that can feed back and make the warming even worse. We’re playing Russian roulette with 5 bullets in the gun.”
Same Message, Fewer ‘Weasel Words’
Scott Denning, an atmospheric scientist at Colorado State University, said the new IPCC report essentially hammers home the same message as all its predecessors, dating back to 1990.
“Each report has less and less weasel words, but it’s still pretty much the same message,” he said. “Adding CO2 to the atmosphere warms up the world.”
One new element of this latest IPCC science assessment is a more regional breakdown of global warming impacts, and some of its conclusions are underlined by current conditions in the Western United States. Water supplies in the West are drying to a trickle after a 20-year drought, dangerous heat waves are lasting longer and thousands of square miles of forest have burned up in the past few years.
Denning said he recently analyzed 40 years of data from a network of 800 snow sensors, finding that about half those sites have lost half of their spring snowpack in the last 40 years.
“Holy crap, we are in trouble if 1 degree Celsius of warming has cost us half our mountain snowpack,” he said. “We’ll rejigger our systems to deliver some water, but we can’t support 75 million people in the West without a mountain snowpack.”
Ida Ploner, a 14-year-old activist with Fridays For Future in Vienna, Austria said the new science report once again shows the urgency of ending carbon dioxide emissions now, especially for her generation, which will live with the consequences of the decisions made today.
“It’s not that it’s going to get just a little warmer,” said Ploner, who has been organizing protests against highway projects that would lead to more greenhouse gas emissions. “This is an existential question. Earth is burning and time is running out.”
The new report could be another wakeup call, she said, but in recent years, other landmark reports have done nothing more than trigger greenwashing campaigns.
“It takes away a bit of hope, when we keep seeing more reports and nothing happens,” she said. “It shouldn’t be my job at 14 to ensure that I have a future. We have leaders for that, but they aren’t doing it, and it’s too important to turn away. We need to show that all of society is mad and that we are going to do something about it.”
The water cycle is intensifying as the climate warms, IPCC report warns – that means more intense storms and flooding
The world watched in July 2021 as extreme rainfall became floods that washed away centuries-old homes in Europe, triggered landslides in Asia and inundated subways in China. More than 900 people died in the destruction. In North America, the West was battling fires amid an intense drought that is affecting water and power supplies.
In a new international climate assessment published Aug. 9, 2021, the Intergovernmental Panel on Climate Change warns that the water cycle has been intensifying and will continue to intensify as the planet warms.
The report, which I worked on as a lead author, documents an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.
Why is the water cycle intensifying?
Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. Plants also take up water from the ground and release it through transpiration from their leaves. In recent decades, there has been an overall increase in the rates of precipitation and evaporation.
A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.
This aspect of climate change is confirmed across all of our lines of evidence: It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.
Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.
Globally, daily extreme precipitation events will likely intensify by about 7% for every 1 degree Celsius (1.8 degrees Fahrenheit) that global temperatures rise.
Many other important aspects of the water cycle will also change in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.
The IPCC does not make policy recommendations. Instead, it provides the scientific information needed to carefully evaluate policy choices. The results show what the implications of different choices are likely to be.
One thing the scientific evidence in the report clearly tells world leaders is that limiting global warming to the Paris Agreement target of 1.5 C (2.7 F) will require immediate, rapid and large-scale reductions in greenhouse gas emissions.
Regardless of any specific target, it is clear that the severity of climate change impacts are closely linked to greenhouse gas emissions: Reducing emissions will reduce impacts. Every fraction of a degree matters.
Humans are unequivocally warming the planet, and that’s triggering rapid changes in the atmosphere, oceans and polar regions, and increasing extreme weather around the world, the Intergovernmental Panel on Climate Change warns in a new report.
The IPCC released the first part of its much anticipated Sixth Assessment Report on Aug. 9, 2021. In it, 234 scientists from around the globe summarized the current climate research on how the Earth is changing as temperatures rise and what those changes will mean for the future.
What are the IPCC report’s most important overall messages in your view?
At the most basic level, the facts about climate change have been clear for a long time, with the evidence just continuing to grow.
As a result of human activities, the planet is changing at a rate unprecedented for at least thousands of years. These changes are affecting every area of the planet.
While some of the changes will be irreversible for millennia, some can be slowed and others reversed through strong, rapid and sustained reductions in greenhouse gas emissions.
But time is running out to meet the ambitious goal laid out in the 2015 international Paris Agreement to limit warming to well below 2 degrees Celsius above preindustrial levels (2 C equals 3.6 degrees Fahrenheit). Doing so requires getting global carbon dioxide emissions on a downward course that reaches net zero around or before 2050.
What are scientists most concerned about right now when it comes to the oceans and polar regions?
Global sea level has been rising at an accelerating rate since about 1970, and over the last century, it has risen more than in any century in at least 3,000 years.
Over the last decade, global average sea level has risen at a rate of about 4 millimeters per year (1.5 inches per decade). This increase is due to two main factors: the melting of ice in mountain glaciers and at the poles, and the expansion of water in the ocean as it takes up heat.
Ice sheets in particular are primarily responsible for the increase in the rate of sea level rise since the 1990s. There is clear evidence tying the melting of glaciers and the Greenland Ice Sheet, as well as ocean warming, to human influence. Sea level rise is leading to substantial impacts on coastal communities, including a near-doubling in the frequency of coastal flooding since the 1960s in many sites around the world.
Since the previous reports, scientists have made substantial advances in modeling the behavior of ice sheets. At the same time, we’ve been learning more about ice sheet physics, including recognizing the potential ways ice sheets can become destabilized. We don’t well understand the potential speed of these changes, but they have the potential to lead to much more rapid ice sheet loss if greenhouse gas emissions grow unchecked.
Sea level change through 2050 is largely locked in: Regardless of how quickly nations are able to lower emissions, the world is likely looking at about 15 to 30 centimeters (6 to 12 inches) of global average sea level rise through the middle of the century.
But beyond 2050, sea level projections become increasingly sensitive to the world’s emissions choices. If countries continue on their current paths, with greenhouse gas emissions likely to bring 3-4 C of warming (5.4-7.2 F) by 2100, the planet will be looking at a most likely sea level rise of about 0.7 meters (a bit over 2 feet). A 2 C (3.6 F) warmer world, consistent with the Paris Agreement, would see lower sea level rise, most likely about half a meter (about 1.6 feet) by 2100.
What’s more, the more the world limits its greenhouse gas emissions, the lower the chance of triggering instabilities in the polar ice sheets that are challenging to model but could substantially increase sea level rise.
Under the most extreme emissions scenario we considered, we could not rule out rapid ice sheet loss leading to sea level rise approaching 2 meters (7 feet) by the end of this century.
Fortunately, if the world limits warming to well below 2 C, it should take many centuries for sea level rise to exceed 2 meters – a far more manageable situation.
Are the oceans or ice nearing any tipping points?
“Tipping point” is a vague term used in many different ways by different people. The IPCC defines tipping points as “critical thresholds beyond which a system reorganizes, in a way that is very fast or irreversible” – for example, a temperature rise beyond which climate dynamics commit an ice sheet to massive loss.
Because the term is so vague, the IPCC generally focuses on characteristics of changes in a system – for example, whether a system might change abruptly or irreversibly – rather than whether it fits the strict dynamic definition of a “tipping point.”
One example of a system that might undergo abrupt changes is the large-scale pattern of ocean circulation known as the Atlantic Meridional Overturning Circulation, or AMOC, of which the Gulf Stream is part. Paleoclimate evidence tells us that AMOC has changed rapidly in the past, and we expect that AMOC will weaken over this century. If AMOC were to collapse, it would make Europe warm more slowly, increase sea level rise along the U.S. Atlantic coast, and shift storm tracks and monsoons. However, most evidence indicates that such a collapse will not happen in this century.
There is mixed evidence for abrupt changes in the polar ice sheets, but clear evidence that changes in the ice sheets can be locked in for centuries and millennia.
If the world succeeds in limiting warming to 1.5 C (2.7 F), we expect to see about 2-3 meters (7-10 feet) of sea level rise over the next 2,000 years; if the planet continues to warm and reaches a 5 C (9 F) increase, we expect to see about 20 meters (70 feet) over the next 2,000 years.
Some people also discuss summer Arctic sea ice – which has undergone substantial declines over the last 40 years and is now smaller than at any time in the past millennium – as a system with a “tipping point.” However, the science is pretty clear that there is no critical threshold in this system. Rather, summer Arctic sea ice area decreases roughly in proportion to the increase in global temperature, and if temperature were stabilized, we would expect sea ice area to stabilize also.
What do scientists know now about hurricanes that they didn’t realize when the last report was written?
Since the last IPCC assessment report in 2013, there has been increasing evidence that hurricanes have grown more intense, and intensified more rapidly, than they did 40 years ago. There’s also evidence that hurricanes in the U.S. are moving more slowly, leading to increased rainfall.
However, it’s not clear that this is due to the effects of greenhouse gases – reductions in particulate pollution have also had important effects.
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The clearest effect of global warming is that a warmer atmosphere holds more water, leading to more extreme rainfall, like that seen during Hurricane Harvey in 2017. Looking forward, we expect to see hurricane winds and hurricane rains continue to increase. It’s still unclear how the overall number of hurricanes will change.
The report involved 234 scientists, and then 195 governments had to agree on the summary for policymakers. Does that broad range of views affect the outcome?
When you’re writing a report like this, a key goal for the scientists is to accurately capture points of both scientific agreement and scientific disagreement.
For example, with respect to ice sheet changes, there are certain processes on which there is broad agreement and other processes where the science is still emerging and there are strong, discordant views. Yet knowing about these processes may be crucially important for decision-makers trying to manage risk.
That’s why, for example, we talk not only about most likely outcomes, but also about outcomes where the likelihood is low or as-yet unknown, but the potential impacts are large.
The IPCC uses a transparent process to produce its report – the authors have had to respond to over 50,000 review comments over the three years we’ve spent writing it. The governments also weigh in, having to approve every line of a concise Summary for Policy Makers that accurately reflects the underlying assessment – oftentimes making it clearer in the process.
I’m very pleased that, as with past reports, every participating government has signed off on a summary that accurately reports the current state of climate science.