Even if we stay under 2C, extreme events -heat, floods, drought – will become more likely in the decades ahead. And if countries do not meet the Paris climate agreement goals, the risks will be even greater
Overall, up to 60% of locations across North America, Europe, East Asia and parts of southern South America would likely see at least a 3x and up to 5x increase in some areas increase in various extreme events, according to a Stanford study published yesterday in the journal Science Advances.
The country pledges to the Paris climate accord may put the world on track to warm by about 3 C, unless significantly greater climate action is promised—and soon.
Events like record-setting heat, extreme rainfall and drought will happen more frequently around the world even if global climate targets are met, new research suggests. And missing those targets could make the risk even worse.
…the pledges world nations have submitted under the Paris Agreement are likely still not enough to keep global temperatures within the 2 C threshold envisioned by the accord. Experts suggest that the pledges may put the world on track to warm by about 3 C, unless significantly greater climate action is promised—and soon.
“In addition to not meeting the global temperature target, those commitments also imply substantial increase in the probability of record-setting events,” said Noah Diffenbaugh, a Stanford University climate researcher and the new study’s lead author. “Not only hot events but wet events, and also in other regions of the world, dry events as well.”…
….Heat records are likely to be among the most sensitive to future climate change. Record-breaking nighttime temperatures have already been increasing across 90 percent of the studied areas, the research suggests, and these records may increase by at least fivefold across half of Europe and a quarter of East Asia.Extreme wet events and milder cold spells are also expected to increase throughout the world, and extreme dry events will see an uptick in certain regions, mainly in the midlatitudes.
Strengthening the Paris pledges could help significantly reduce the risks of extreme climate events, the new research suggests, although it warns that these events will still become more frequent in the future, even if temperature increases stay under 2 C.
….The findings, overall, carry a double warning. First, even with aggressive climate action, extreme climate events are likely to increase throughout much of the world—and human societies should brace themselves for that future, no matter what. But those mitigation efforts are still sorely needed, the research also suggests. Without them, the risks could be far more intense.
Noah S. Diffenbaugh, Deepti Singh, and Justin S. Mankin. Unprecedented climate events: Historical changes, aspirational targets, and national commitments. Science Advances, 14 Feb 2018 DOI: 10.1126/sciadv.aao3354
Also called post-fire debris flows, these mudslides form when water rushing down slopes picks up dirt, burnt trees, rocks, and other debris (like cars), reaching speeds of more than 35 miles per hour. “When you mix a lot of mud, water, and boulders, it certainly can be quite catastrophic,” says Dennis Staley, a scientist with the US Geological Survey Landslide Hazards Program. The slurries can start with almost no warning after as little as a third of an inch of rain in just 30 minutes — especially on slopes scorched by fires. After fires blazed across more than half a million acres this fall in California’s worst fire season on record, it’s not hard to find burnt land.
Rainfall changes caused by global warming will increase river flood risks across the globe. Already today, fluvial floods are among the most common and devastating natural disasters. Scientists have now calculated the required increase in flood protection until the 2040s worldwide, breaking it down to single regions and cities. They find that the need for adaptation is greatest in the US, parts of India and Africa, Indonesia, and in Central Europe including Germany. Inaction would expose many millions of people to severe flooding.
…”We have been surprised to find that even in developed countries with good infrastructure the need for adaptation is big,” says co-author Anders Levermann,
….An increase in river flood risks over the next 2-3 decades will be driven by the amount of greenhouse-gases already emitted into the atmosphere, hence it does not depend on whether or not we limit global warming.”
However, it is clear that without limiting human-caused warming to well below 2 degrees Celsius, river flood risks in our century will increase in many regions to a level that we cannot adapt to,” says Levermann. “To keep people safe climate-change-induced risks must be taken seriously and money must be spent for adaptation. If we act now, we can protect against the risks of the next two decades. But further climate change must be limited by cutting greenhouse gas emissions from fossil fuels to avoid risks that surpass our abilities to adapt.”…
Sven N. Willner, Anders Levermann, Fang Zhao, Katja Frieler. Adaptation required to preserve future high-end river flood risk at present levels. Science Advances, 2018; 4 (1): eaao1914 DOI: 10.1126/sciadv.aao1914
Abstract: Earth’s surface temperature will continue to rise for another 20 to 30 years even with the strongest carbon emission reduction currently considered. The associated changes in rainfall patterns can result in an increased flood risk worldwide. We compute the required increase in flood protection to keep high-end fluvial flood risk at present levels. The analysis is carried out worldwide for subnational administrative units. Most of the United States, Central Europe, and Northeast and West Africa, as well as large parts of India and Indonesia, require the strongest adaptation effort. More than half of the United States needs to at least double their protection within the next two decades. Thus, the need for adaptation to increased river flood is a global problem affecting industrialized regions as much as developing countries.
California is spending billions to protect the millions at risk of a megaflood, but thanks to climate change, it’s too little too late.
California’s megaflood isn’t the stuff of fantasy flicks, it’s based on a 200-plus page piece of science that tested the limits of what was humanly possible in disaster prediction eight years ago known as the ARkStorm scenario… designed with an explicit purpose in mind: to objectively quantify and qualify the California’s threat of a coming flood that only a small group of niche scientists knew the bounds of at the time.
Climate change is increasing the chances that not only will these rare flood events become the norm in California, but that in the decades to come they could be even more intense than the one predicted here.
….The water will linger for days, weeks and in some places months. By the time it subsides the final toll will redefine the word catastrophe: More than $850 billion in damages (adjusted for inflation), more than four times costlier than Katrina, the costliest natural disaster in U.S. history. More than a million people forced to flee their homes in one of the largest evacuations in U.S. history, and many who return will return to nothing.
This is California’s megaflood, a catastrophe not seen in a lifetime, but one scientists, disaster experts and officials know is coming in a warming world. No one knows when it will come, but it has happened in centuries past, and these are just some of its scientifically predicted and realistic impacts in modern day California.
Now climate change is increasing the chances that not only will these rare flood events become the norm in California, but that in the decades to come they could be even more intense than the one predicted here.
California’s once-in-centuries catastrophe is no longer a future problem. Billions of dollars of local, state and federal action to bolster the state’s outdated flood protections have come too late and isn’t enough to protect the millions of Californians currently at risk of such an event and the millions more who will be at risk in the decades to come.
Californians are playing climate catch-up in a state that’s ground zero for climate change’s future megafloods…..
Of that $550 million, $350 million is designated to the DWR for flood management in the Central Valley, including $50 million specifically set aside for levee repairs in the San Joaquin and Sacramento Deltas.
Some $100 million is available for grants for “stormwater, mudslide, and other flash-flood-related protections” and another $100 million for grants for “multibenefit projects in urbanized areas to address flooding” statewide.
But the bill’s primary goal is investment in parks, particularly in communities without access to parks, leaving flood protection as a footnote. The bill’s author, Kevin De León called it “the single largest investment in the history of the United States to park-starved communities.”
The proposed November bond, drafted by the former deputy secretary of the state Natural Resources Agency, Jerry Meral, aims to be “complementary” to the June ballot measure and “make sure that no critical problem was totally ignored,” filling in some of the gaps of flood protection funding from the June bond. …
Source: U.S. Army Corps of Engineers, California Department of Water Resources (2013)
This January 1862 photo shows floodwaters along K Street looking west from 4th street in Sacramento after the Great Flood of 1861-62. (California State Library, DWR)
Changing Climate, Changing Floods
Climate change’s expected increase in temperatures and extreme precipitation will combine to produce more epic floods in California. This graphic shows how warmer temperatures will melt snowpack quicker and dump more rain and less snow on mountain ranges, leading to more prolific floods. Source: California Department of Water Resources 2017
One of the 23,000 homes flooded during the 1997 floods in California. (Norm Hughes/California Department of Water Resources)
..The study found that timing plays a key role in how well wet soils retain organic matter. While soils with consistently high moisture content do retain organic matter over the long term, soils may actually lose organic matter during shorter spans of flooding. The findings have implications for agricultural fields that are poorly drained or flood for a few weeks of the year before drying out, Hall said. The study also shows that wetlands, thought of as a useful tool for conservation and carbon sequestration, may require consistent flooding to realize environmental benefits from organic matter accumulation….
…”We found that periodically wet soils don’t necessarily protect organic matter from decomposition and may lead to losses, at least over a timescale of weeks to months,” he said.
The study drew on research conducted in an ISU laboratory. The researchers took soil samples from a central Iowa cornfield and subjected the sample to various conditions before conducting chemical analyses.
Hall said future research should widen in scope and include field experiments as well as laboratory-based work. He said he wants to test how various drainage techniques influence organic matter loss as well as pinpoint the length of time required for wet soil to realize environmental benefits….
Wenjuan Huang, Steven J. Hall. Elevated moisture stimulates carbon loss from mineral soils by releasing protected organic matter. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-01998-z
Sacramento is more vulnerable to catastrophic flooding than any other major city in the United States except New Orleans, according to federal officials, a threat created by the city’s sunken geography.
…Models show a levee failure could submerge parts of this inland metropolis [Sacramento] under as much as 20 feet of water. As Northern Californians are recovering from wildfires and sifting through homes reduced to ash, officials in the state’s capital are struggling to prevent another type of natural disaster….
…Levees and other flood defenses here and in the surrounding Central Valley have amassed up to $21 billion in needed repairs and upgrades, while Sacramento’s population has continued to grow. Just days before Hurricane Harvey slammed into Texas and flooded Houston, a report from the California Department of Water Resources warned that “many flood facilities” in the Central Valley “face an unacceptably high chance of failure.”…
….If a levee were to break along the American River, which empties into the Sacramento River near downtown, water would start flowing into the city.
Although floodgates could be quickly deployed to protect downtown Sacramento from a life-threatening deluge, the water would eventually seep in from other directions, covering much of the area in several feet of water, said Roger Ince, a Sacramento emergency coordinator.
The water would continue flowing south and deposit more than 20 feet of water in the Pocket neighborhood, where about 20,000 people live in one- and two-story homes….
….In a 2010 report called “Overview of the ARkStorm Scenario,” more than two dozen scientists concluded that two back-to-back storms of similar strength could slam into California and submerge 25 percent of the state underwater.
“This isn’t science fiction,” said one of the authors, Keith Porter, a research professor at the University of Colorado at Boulder. “It’s a very realistic scenario, and it could happen at any time.”
Jeffrey Mount, a senior fellow and water resources specialist at the Public Policy Institute of California, said such projections raise serious questions about continued development in California’s flood plain, a debate that has been playing out in Sacramento’s Natomas neighborhood, where thousands of new homes are planned…
Planting trees can reduce flood risk, but a high intensity forest land use, such as grazing, can counteract the positive effect
Infiltration rates were between ten and a hundred times higher under trees, when the forested area remained relatively undisturbed, compared with adjacent pasture
Forest buffer zones, with restricted access, strategically placed to intercept surface runoff before it reaches the stream may be more effective than larger scale planting when the forested areas are used for other purposes
As the frequency and severity of flooding becomes an increasing problem, land managers are turning to natural flood management measures, such as tree planting, to reduce the risk. When rainfall exceeds the rate at which water can enter the soil it flows rapidly over the land’s surface into streams and rivers. Trees can help to reduce the risk of surface runoff by increasing the number of large pores in the soil through which water can drain more easily. Land use, such as grazing, also affects the soil’s ability to absorb water; however, while the effect of land use on surface runoff has been well studied in grasslands, little is known about the effect of land use in forests.
…Researchers found that infiltration rates were between ten and a hundred times higher under trees, when the forested area remained relatively undisturbed, compared with adjacent pasture. Where sheep were allowed to graze under the trees there was no observable difference from the pasture.
They also compared forest types — conifer forest planted with Scots Pine and broadleaved forest planted with sycamore — and found that infiltration rates were significantly higher under Scots Pine than under sycamore, but only when the forest was ungrazed…
…”Tree planting can make an important contribution to flood risk management, but forest buffer zones, with restricted access, strategically placed to intercept surface runoff before it reaches the stream may be more effective than larger scale planting when the forested areas are used for other purposes.”…
K.R.Chandler, C.J.Stevens, A.Binley, A.M.Keith. Influence of tree species and forest land use on soil hydraulic conductivity and implications for surface runoff generation. Geoderma, 2017 DOI: 10.1016/j.geoderma.2017.08.011
As the recent floods from Bangladesh to Texas show, it’s not just the unprecedented magnitude of storms that can cause disaster: it’s urbanisation.
From sponge cities in China to ‘berms with benefits’ in New Jersey and floating container classrooms in the slums of Dhaka, we look at a range of projects that treat storm water as a resource rather than a hazard.
They call it “pave, pipe, and pump”: the mentality that has dominated urban development for over a century. Along with the explosion of the motorcar in the early 20th century came paved surfaces. Rainwater – instead of being sucked up by plants, evaporating, or filtering through the ground back to rivers and lakes – was suddenly forced to slide over pavements and roads into drains, pipes and sewers. Their maximum capacities are based on scenarios such as 10-year storms. And once they clog, the water – with nowhere else to go – simply rises.
The reality of climate change and more frequent and intense downpours has exposed the hubris of this approach. As the recent floods from Bangladesh to Texas show, it’s not just the unprecedented magnitude of storms that can cause disaster: it’s urbanisation.
…With climate change both a reality and threat, many architects and urbanists are pushing creative initiatives for cities that treat stormwater as a resource, rather than a hazard….
…In China, the government has commissioned the construction of 16 “Sponge Cities” to pilot solutions for the freshwater scarcity and flooding suffered in many cities as a result of rapid urbanisation. Chicago architectural firm UrbanLab was commissioned to design the masterplan for Yangming Archipelago in Hunan province: a new centre within the larger city of Changde, devised as a “new model for the future”.
The area, a low-lying land river basin that experiences heavy rainfall, is regularly flooded. Instead of incorporating defences against water, UrbanLab put space for it to flow at the centre of its urban plan, putting major buildings on islands in an enormous central lake. Canal-lined streets that UrbanLab call “Eco-boulevards” connect the eight districts – the process is visualised in this video.
UrbanLab says their vision combines a dense metropolis with a nature setting: “As a functional center, Yangming Archipelago will serve as an urban model, we expect it to lead the way to a new way of thinking about the city of the future.”
Permeable pavements: Chicago’s ‘green alleys’
Rainwater travels through the self-cleaning, pollution-reducing sidewalk before going on to feed surrounding plants…
…In New Jersey and New York…in response to Sandy, ZUS partnered with MIT’s Center for Advanced Urbanism and De Urbanisten to devise New Meadowlands: a masterplan for combining flood resilience with recreational amenities through marshes and a system of parallel raised banks called berms.
Between the outer berm and the sea, the restored wetlands would soak up seawater and slow down tidal waves, preventing them from hitting the dikes at high speed. The stretch of berms would serve as a wildlife refuge, filling up with rainwater during periods of heavy rain before draining out. And on the insider of the inner berm, ditches and ponds would retain rainwater, preventing it from causing sewers to overflow….
…California is facing its own threat of bigger and more destructive storms. Mounting research, much of it done in the wake of the near-record rains that pulled California out of a five-year drought this past winter, shows that seasonal soakers may not come as often as they used to, but could pack more punch when they do arrive.