Featured image: Lake Powell, photographed April 12, 2017. The white ‘bathtub ring’ at the cliff base indicates how much higher the lake reached at its peak, nearly 100 feet above the current level. Patti Weeks
The nation’s two largest reservoirs, Lake Mead on the Arizona/Nevada border and Lake Powell on the Arizona/Utah border, were brim full in the year 2000. Four short years later, they had lost enough water to supply California its legally apportioned share of Colorado River water for more than five years. Now, 17 years later, they still have not recovered.
This ongoing, unprecedented event threatens water supplies to Los Angeles, San Diego, Phoenix, Tucson, Denver, Salt Lake City, Albuquerque and some of the most productive agricultural lands anywhere in the world. It is critical to understand what is causing it so water managers can make realistic water use and conservation plans.
While overuse has played a part, a significant portion of the reservoir decline is due to an ongoing drought, which started in 2000 and has led to substantial reductions in river flows. Most droughts are caused by a lack of precipitation. However, our published research shows that about one-third of the flow decline was likely due to higher temperatures in the Colorado River’s Upper Basin, which result from climate change.
This distinction matters because climate change is causing long-term warming that will continue for centuries. As the current “hot drought” shows, climate change-induced warming has the potential to make all droughts more serious, turning what would have been modest droughts into severe ones, and severe ones into unprecedented ones.
The Colorado River is about 1,400 miles long and flows through seven U.S. states and into Mexico. The Upper Colorado River Basin supplies approximately 90 percent of the water for the entire basin. It originates as rain and snow in the Rocky and Wasatch mountains. USGS
How climate change reduces river flow
In our study, we found the period from 2000 to 2014 is the worst 15-year drought since 1906, when official flow measurements began. During these years, annual flows in the Colorado River averaged 19 percent below the 20th-century average.
During a similar 15-year drought in the 1950s, annual flows declined by 18 percent. But during that drought, the region was drier: rainfall decreased by about 6 percent, compared to 4.5 percent between 2000 and 2014. Why, then, is the recent drought the most severe on record?
The answer is simple: higher temperatures. From 2000 to 2014, temperatures in the Upper Basin, where most of the runoff that feeds the Colorado River is produced, were 1.6 degrees Fahrenheit higher than the 20th-century average. This is why we call this event a hot drought. High temperatures continued in 2015 and 2016, as did less-than-average flows. Runoff in 2017 is expected to be above average, but this will only modestly improve reservoir volumes.
High temperatures affect river levels in many ways. Coupled with earlier snow melt, they lead to a longer growing season, which means more days of water demand from plants. Higher temperatures also increase daily plant water use and evaporation from water bodies and soils. In sum, as it warms, the atmosphere draws more water, up to 4 percent more per degree Fahrenheit from all available sources, so less water flows into the river. These findings also apply to all semi-arid rivers in the American Southwest, especially the Rio Grande.
The combined contents of the nation’s two largest reservoirs, Lake Mead and Lake Powell, since their initial fillings. The large decline since 2000 is shaded brown for 2000-2014, our 15-year study period, and pink for the continuing drought in 2015-2016. The loss was significantly influenced by record-setting temperatures, unlike a similar 15-year drought in the 1950s which was driven by a lack of precipitation. Bradley Udall, Author provided
A hotter, drier future
Knowing the relationship between warming and river flow, we can project how the Colorado will be affected by future climate change. Temperature projections from climate models are robust scientific findings based on well-tested physics. In the Colorado River Basin, temperatures are projected to warm by 5°F, compared to the 20th-century average, by midcentury in scenarios that assume either modest or high greenhouse gas emissions. By the end of this century, the region would be 9.5°F warmer if global greenhouse gas emissions are not reduced.
Using simple but strong relationships derived from hydrology models, which were buttressed by observations, we and our colleagues calculated how river flows are affected by higher temperatures. We found that Colorado River flows decline by about 4 percent per degree Fahrenheit increase, which is roughly the same amount as the increased atmospheric water vapor holding capacity discussed above. Thus, warming could reduce water flow in the Colorado by 20 percent or more below the 20th-century average by midcentury, and by as much as 40 percent by the end of the century. Emission reductions could ease the magnitude of warming by 2100 from 9.5°F to 6.5°F, which would reduce river flow by approximately 25 percent.
Large precipitation increases could counteract the declines that these all-but-certain future temperature increases will cause. But for that to happen, precipitation would have to increase by an average of 8 percent at midcentury and 15 percent by 2100.
The American Canal carries water from the Colorado River to farms in California’s Imperial Valley. Adam Dubrowa, FEMA/Wikipedia
On a year-in, year-out basis, these large increases would be substantial. The largest decade-long increases in precipitation in the 20th century were 8 percent. When such an increase occurred over 10 years in the Colorado Basin in the 1980s, it caused large-scale flooding that threatened the structural stability of Glen Canyon Dam, due to a spillway failure not unlike the recent collapse at California’s Oroville Dam.
For several reasons, we think these large precipitation increases will not occur. The Colorado River Basin and other areas around the globe at essentially the same latitudes, such as the Mediterranean region and areas of Chile, South Africa and Australia, are especially at risk for drying because they lie immediately poleward of the planet’s major deserts. These deserts are projected to stretch polewards as the climate warms. In the Colorado River basin, dry areas to the south are expected to encroach on some of the basin’s most productive snow and runoff areas.
Moreover, climate models do not agree on whether future precipitation in the Colorado Basin will increase or decrease, let alone by how much. Rain gauge measurements indicate that there has not been any significant long-term change in precipitation in the Upper Basin of the Colorado since 1896, which makes substantial increases in the future even more doubtful.
Megadroughts, which last anywhere from 20 to 50 years or more, provide yet another reason to avoid putting too much faith in precipitation increases. We know from tree-ring studies going back to A.D. 800 that megadroughts have occurred previously in the basin.
March of 2017 was the warmest March in Colorado history, with temperatures a stunning 8.8°F above normal. Snowpack and expected runoff declined substantially in the face of this record warmth. Clearly, climate change in the Colorado River Basin is here, it is serious and it requires multiple responses.
It takes years to implement new water agreements, so states, cities and major water users should start to plan now for significant temperature-induced flow declines. With the Southwest’s ample renewable energy resources and low costs for producing solar power, we can also lead the way in reducing greenhouse gas emissions, inducing other regions to do the same. Failing to act on climate change means accepting the very high risk that the Colorado River Basin will continue to dry up into the future.
22 years ago on this very continent was brought to the negotiating table the crisis of climate change. Many evasive proposals, claims to turn the crisis into an opportunity for business, denials, omissions and grand tragedies embody the climate crisis in the territories. A balance of 22 years of indifference and cynicism.
Governments and transnational interests continue to invest in the destruction of forests, rivers, oceans, jungles, mashlands, mountains and deserts; living spaces that end up being sacrificed in the name of “development” and “progress”.
In these 22 years, we are far from believing that the solution will come from governments; that the market will contribute to environmental conservation, or that the commodification of nature will protect the climate.
Our view is the way of indigenous communities that have known to preserved ecosystems, in farming communities who struggle to protect their lands, in women who work caringly in the rivers, in the children that keep alive their capacity of fascination with nature, and in the inhabitants of large cities who know that they have been robbed from nature since birth. Our guardians.
Us, the very ones who we are, have come here to convince you (and convince ourselves of the certainty that the world we want already exists), as there are colors of the earth, the suns that shine us, and the ways of our guardians that defend the territories around the globe.
This is why we call to find ourselves on the road to the COP20, to join our histories, our views, and our ways that demand climate justice under these guiding principles:
1. Maintain the fossil fuels underground is not only a priority to halting environmental devastation, but to end one of the evils that has so hurt and changed the pace of the climate in very few decades.
2. Ban the financialization of forests and the commodification of the functions of nature, as they are not a solutions to reduce emissions of carbon gases into the atmosphere; strategies which represent false solutions that have increased the destruction of ecosystems, the breakdown of communitarian social fabric and organization.
3. Water, as a common good can no longer be conceived as a commodity. Dams and hydroelectric dams are part of the mining and energy industries. The production of hydroelectric power is what keeps widening the gap of environmental devastation.
The aggressiveness with which the occupation of territories intends to expand itself does not depend on the political color of governments, but rather is linked to the perpetuation of the capitalist system under the same logic of accumulation at the expense of nature and communities.
Therefore, it becomes more urgent to find one another, Us.
They are the ones who will find the solutions- It’s us, the unadaptaded, the unadaptable climate change- It is us that can and must contain the war against nature.
Climate change may be stunting fish growth, a new study has said. Fish sizes in the North Sea have shrunk dramatically, and scientists believe warmer ocean temperatures and less oxygenated water could be the causes.
The body sizes of several North Sea species have decreased by as much as 29 percent over a period of four decades, according to the report, published in the April issue of Global Change Biology.
The report presents evidence gathered as researchers followed six commercial fish species in the North Sea over 40 years. Their evidence showed that as water temperatures increased by 1 to 2 degrees Celsius, an accompanying reduction in fish size was observed.
It is generally accepted among scientists that decreased body size is a universal response to increasing temperatures, known as the “temperature size rule,” the report said. But before this report, led by scientists at Scotland’s University of Aberdeen, there was no empirical evidence showing this response in marine fish species.
The scientists warned that fish stunting cannot be unequivocally blamed on temperature changes, but they did observe fish stunting across varying species and backgrounds that coincided with a period of increasing ocean temperature.
Other factors that could have influenced fish size include fisheries-induced evolution and intensive commercial fishing — which favors larger specimens. But, the scientists said, these causes would not be likely to affect growth rates across species, which was observed in the North Sea study.
Scientists at the University of Washington have been working on a similar study, looking at many species of fish from Alaska to California. Tim Essington, an associate professor of aquatic and fishery sciences at UW who is working on the study, said he was looking into whether changes in fish body size could be related to environmental parameters.
“We haven’t seen the same strong response,” Essington told Al Jazeera. “But we have seen variation in the sizes of some stocks, like halibut. Its body size has been shrinking sharply over the past 10 years, and has resulted in reduced catch quotas and higher prices at the supermarket.”
He said various factors explain why UW results were different from those of the Scottish team. University of Aberdeen scientists were looking at a much more localized area and a unique data set, and had many more years of data to make comparisons.
Overall, Essington said the Aberdeen findings represented a plausible hypothesis that should be looked at more closely, and that warmer temperatures could explain the stunting.
“Fish aren’t any different than us. It’s all about the difference between how much we eat and how much energy we expend. And they’re arguing that temperature is changing the fishes’ energy versus expension rates,” which could result in smaller sizes, Essington said.
The Aberdeen findings echoed earlier model-derived predictions that fish would shrink in warmer waters. Those projections for future fish size reduction are already being seen in the North Sea, scientists said.
The first global projection of the potential for fish stunting in warmer, less oxygenated oceans was carried out by the University of British Columbia in 2012, and published in the journal Nature Climate Change.
The projection said changes in ocean and climate systems by 2050 could result in fish that are 14 to 24 percent smaller globally.
“It’s a constant challenge for fish to get enough oxygen from water to grow, and the situation gets worse as fish get bigger,” said Daniel Pauly, principal investigator with the University of British Columbia’s Sea Around Us Project, and the co-author of the UBC study.
The study warned that strategies must be developed to curb greenhouse-gas emissions or risk disrupting food security, fisheries and the very way ocean ecosystems work.
Time is running out for Australia’s iconic Great Barrier Reef, with climate change set to wreck irreversible damage by 2030 unless immediate action is taken, marine scientists said Thursday.
In a report prepared for this month’s Earth Hour global climate change campaign, University of Queensland reef researcher Ove Hoegh-Guldberg said the world heritage site was at a turning point.
“If we don’t increase our commitment to solve the burgeoning stress from local and global sources, the reef will disappear,” he wrote in the foreword to the report.
“This is not a hunch or alarmist rhetoric by green activists. It is the conclusion of the world’s most qualified coral reef experts.”
Hoegh-Guldberg said scientific consensus was that hikes in carbon dioxide and the average global temperature were “almost certain to destroy the coral communities of the Great Barrier Reef for hundreds if not thousands of years”.
“It is highly unlikely that coral reefs will survive more than a two degree increase in average global temperature relative to pre-industrial levels,” he said.
“But if the current trajectory of carbon pollution levels continues unchecked, the world is on track for at least three degrees of warming. If we don’t act now, the climate change damage caused to our Great Barrier Reef by 2030 will be irreversible.”
The Great Barrier Reef, one of the most biodiverse places on Earth, teems with marine life and will be the focus of Australia’s Earth Hour—a global campaign which encourages individuals and organisations to switch off their lights for one hour on April 29 for climate change.
The report comes as the reef, considered one of the most vulnerable places in the world to the impacts of climate change, is at risk of having its status downgraded by the UN cultural organisation UNESCO to “world heritage in danger”.
Despite threats of a downgrade without action on rampant coastal development and water quality, Australia in December approved a massive coal port expansion in the region and associated dumping of dredged waste within the marine park’s boundaries.
The new report “Lights Out for the Reef“, written by University of Queensland coral reef biologist Selina Ward, noted that reefs were vulnerable to several different effects of climate change; including rising sea temperatures and increased carbon dioxide in the ocean, which causes acidification.
It found the rapid pace of global warming and the slow pace of coral growth meant the reef was unlikely to evolve quickly enough to survive the level of climate change predicted in the next few decades.
As if ocean acidification and climate change weren’t troubling enough (both of which are caused by still-rising carbon emissions), new research published in Nature finds that ocean acidification will eventually exacerbate global warming, further raising the Earth’s temperature.
Scientists have long known that tiny marine organisms—phytoplankton—are central to cooling the world by emitting an organic compound known as dimethylsulphide (DMS). DMS, which contains sulfur, enters the atmosphere and helps seed clouds, leading to a global cooling effect. In fact, in the past scientists have believed that climate change may actually increase DMS emissions, and offset some global warming, but they did not take into account the impact of acidification.
Researchers, headed by Katharina Six with the Max Planck Institute for Meteorology, tested how acidification affects phytoplankton in the laboratory by lowering the pH (i.e. acidifying) in plankton-filled water tanks and measuring DMS emissions. When they set the ocean acidification levels for what is expected by 2100 (under a moderate greenhouse gas scenario) they found that cooling DMS emissions fell.
Plugging the results into global modeling system, Six says, “we get an extra warming of 0.23 to 0.48 degree Celsius from the proposed impact [by 2100],” adding that “less sulphur results in a warming of the Earth surface.” This creates a positive feedback loop that will likely have impacts that are anything but positive, according to scientists.
To date, the world has warmed approximately 0.8 degrees Celsius in the last century with a variety of impacts including worsening severe weather, rising sea levels, melting glaciers and sea ice, and imperiled species.
Six also notes that a warmer world does not necessarily mean a more productive world for phytoplankton as has been argued by researchers in the past.
“In former times it was assumed that phytoplankton potentially growth better in a warmer ocean,” she explained to mongabay.com. “However, the basis for plant growth is the supply with nutrients. As the oceans will stabilize in the warmer climate, fewer nutrients will be transported into the sunlight zone. Earth system models, like the MPI-ESM that was used for our study, project a decrease in primary production of 17 percent at the end of this century for a moderate climate scenario. The impact from climate change alone led to a decrease in DMS emission of 7 percent.”
The results are still preliminary as researchers have yet to test how DMS emissions will by impacted in tropical and subtropical waters, focusing to date on polar and temperate waters. In addition, further modeling should be done in order to understand possible uncertainties according to Six.
Still, the evidence is strong enough that the researchers write in the paper that “this potential climate impact mechanism of ocean acidification should be considered in projections of future climate change.” Essentially raising current estimates for a moderate climate scenario by around 10 percent.
Ocean acidification, which has been dubbed “climate change’s equally evil twin” by U.S. National Oceanic and Atmospheric Administration (NOAA)’s Jane Lubchenco, is expected to have largely negative impacts on many marine species, including dissolving the shells of crustaceans and molluscs, hampering coral reefs, and even changing how far fish can hear.
So, how do we stop this from happening?
“There is only one answer,” Katharina Six told mongabay.com, “the abatement of fossil fuel emissions.”
It takes years to implement new water agreements, so states, cities and major water users should start to plan now for significant temperature-induced flow declines. With the Southwest’s ample renewable energy resources and low costs for producing solar power, we can also lead the way in reducing greenhouse gas emissions, inducing other regions to do the same. Failing to act on climate change means accepting the very high risk that the Colorado River Basin will continue to dry up into the future.
