Adventures in Unsustainability

Greetings

      I find myself in Tucson,, AZ so naturally I am inclined to reflect on local conditions.    Sustainability  or  it's opposite, can be viewed from a number of perspectives.

 Here, of course, water sticks out.   

    Tucson has relied on groundwater for much of its history.  And the water table has responded by running away!   Now the water table is over 150 down, and would continue to drop, except that the city has begun importing water from the Colorado River - 300 miles away, pumping it 1500 feet uphill.  

     Between 1975 and 2000, the population of this area increased by 90%.  Local planners expect the Tucson area population to increase by another 80% by 2040.  This may not work out if the Colorado River doesn't cooperate.  For instance see this report from this August notes that the current 13 year western US  drought is limiting water availability..  

" More than a dozen years of drought have begun to extract a heavy toll from water supplies in the West, where a report released last week forecast dramatic cuts next year in releases between the two main reservoirs on the Colorado River, the primary source of water for tens of millions of people across seven western states.

After studying the problems facing the river for the past two years, the U.S. Bureau of Reclamation – the agency charged with managing water in the West – announced Friday that it would cut the amount of water released next year by Lake Powell in Arizona by 750,000 acre-feet, enough to supply about 1.5 million homes.

It marks the first reduction in water flows since the mid 1960s, when the lake was created by the construction of Glen Canyon Dam. "This is the worst 14-year drought period in the last hundred years," said Larry Wolkoviak, director of the bureau's Upper Colorado Region.

The move could trigger an "unprecedented water crisis within the next few years," the business coalition group Protect the Flows told USA Today, as reductions could have major ramifications for farmers and businesses downstream that depend on those flows, as well as on hydroelectric power generation.

This region has known longer dry spells, known as "mega droughts".  These, of course, pre dated climate change

"Tree ring data show that decades-long droughts have occurred before humans started emitting greenhouse gases that fuel climate change. Long-lasting drought events have been tied to fluctuations in ocean conditions, which can alter large-scale weather patterns. For example, when the tropical Pacific Ocean is cooler than average, but the Atlantic Ocean is unusually mild — as has been the case during the past several years — there is a higher risk of drought in parts of the West and Central U.S. 

The area of the West that was affected by severe drought in the Medieval period was much higher and much longer than the current drought, tree ring data show.

It is “indeed pretty scary,” Cook said. “One lasted 29 years. One lasted 28 years. They span the entire continental United States.”

But  droughts, and lower river flows,  are definitely more likely as a result of climate change.  

"Climate change will likely decrease the river’s flow by 5 to 20 percent in the next 40 years, says geoscientist Brad Udall, director of the University of Colorado Western Water Assessment. Less precipitation in the Rocky Mountains will yield less water to begin with. Droughts will last longer. Higher overall air temperatures will mean more water lost to evaporation. “You’re going to see earlier runoff and lower flows later in the year,” so water will be more scarce during the growing season, says "

Read more:

Another report suggests a reductions of Colorado River flows as high as 50% by 2050.

And these assessments are probably conservative,  as they may only assume an average increase of 2 degrees by 2100.  .  A  recent paper in Nature suggests that 4 degrees by 2100 is more likely.

"Professor Steven Sherwood, at the University of New South Wales, in Australia, who led the new work, said: "This study breaks new ground twice: first by identifying what is controlling the cloud changes and second by strongly discounting the lowest estimates of future global warming in favour of the higher and more damaging estimates."

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  http://www.theguardian.com/environment/2013/dec/31/planet-will-warm-4c-2100-climate?

Temperature rises resulting from unchecked climate change will be at the severe end of those projected, according to a new scientific study.

The scientist leading the research said that unless emissions of greenhouse gases were cut, the planet would heat up by a minimum of 4C by 2100, twice the level the world's governments deem dangerous.

The research indicates that fewer clouds form as the planet warms, meaning less sunlight is reflected back into space, driving temperatures up further still. The way clouds affect global warming has been the biggest mystery surrounding future climate change.

Professor Steven Sherwood, at the University of New South Wales, in Australia, who led the new work, said: "This study breaks new ground twice: first by identifying what is controlling the cloud changes and second by strongly discounting the lowest estimates of future global warming in favour of the higher and more damaging estimates."

"4C would likely be catastrophic rather than simply dangerous," Sherwood told the Guardian. "For example, it would make life difficult, if not impossible, in much of the tropics, and would guarantee the eventual melting of the Greenland ice sheet and some of the Antarctic ice sheet", with sea levels rising by many metres as a result.

The research is a "big advance" that halves the uncertainty about how much warming is caused by rises in carbon emissions, according to scientists commenting on the study, published in the journal Nature. Hideo Shiogama and Tomoo Ogura, at Japan's National Institute for Environmental Studies, said the explanation of how fewer clouds form as the world warms was "convincing", and agreed this indicated future climate would be greater than expected. But they said more challenges lay ahead to narrow down further the projections of future temperatures.

Scientists measure the sensitivity of the Earth's climate to greenhouse gases by estimating the temperature rise that would be caused by a doubling of CO2 in the atmosphere compared with pre-industrial levels – as is likely to happen within 50 years, on current trends. For two decades, those estimates have run from 1.5C to 5C, a wide range; the new research narrowed that range to between 3C and 5C, by closely examining the biggest cause of uncertainty: clouds.

The key was to ensure that the way clouds form in the real world was accurately represented in computer climate models, which are the only tool researchers have to predict future temperatures. When water evaporates from the oceans, the vapour can rise over nine miles to form rain clouds that reflect sunlight; or it may rise just a few miles and drift back down without forming clouds. In reality, both processes occur, and climate models encompassing this complexity predicted significantly higher future temperatures than those only including the nine-mile-high clouds.

"Climate sceptics like to criticise climate models for getting things wrong, and we are the first to admit they are not perfect," said Sherwood. "But what we are finding is that the mistakes are being made by the models which predict less warming, not those that predict more."

He added: "Sceptics may also point to the 'hiatus' of temperatures since the end of the 20th century, but there is increasing evidence that this inaptly named hiatus is not seen in other measures of the climate system, and is almost certainly temporary."

Global average air temperatures have increased relatively slowly since a high point in 1998 caused by the ocean phenomenon El Niño, but observations show that heat is continuing to be trapped in increasing amounts by greenhouse gases, with over 90% disappearing into the oceans. Furthermore, a study in November suggested the "pause" may be largely an illusion resulting from the lack of temperature readings from polar regions, where warming is greatest.

Sherwood accepts his team's work on the role of clouds cannot definitively rule out that future temperature rises will lie at the lower end of projections. "But," he said, for that to be the case, "one would need to invoke some new dimension to the problem involving a major missing ingredient for which we currently have no evidence. Such a thing is not out of the question but requires a lot of faith."

He added: "Rises in global average temperatures of [at least 4C by 2100] will have profound impacts on the world and the economies of many countries if we don't urgently start to curb our emissions."