The "runaway greenhouse"—which is thought to have happened on Venus in the past—is basically a climate change worst-case scenario: We reach a critical point where the atmosphere is so thick with greenhouse gases that no sunlight can escape back into space, the planet heats uncontrollably, the oceans evaporate completely, and things get, well, pretty uncomfortable, to put it mildly.
Plans to boost food and energy production in one of West Africa’s most rapidly populating regions are likely to be put in jeopardy by water shortages brought about by rising temperatures, falling rainfall and increased evaporation, says a new report.
The Volta River is one of Africa’s main waterways. More than 24 million people in Ghana, Burkina Faso, Benin, Ivory Coast, Mali and Togo depend on the river and its tributaries for water. The output of hydro-electric plants on the river is also a key element in providing power for irrigation systems and for driving the region’s industrial growth.
The study, The Water Resource Implications of Changing Climate in the Volta River Basin by the International Water Management Institute and partner organisations, says there are indications that temperatures will rise by up to 3.6°C in the Volta River Basin over the next century – leading to significant water loss due to evaporation – while rainfall in the region could drop by 20%.
As a result water flows in the Volta and its tributaries could fall by 45%, “depriving the basin of water that countries are counting on to drive turbines and feed farms” says the study.
It says the decrease in water flows means that by 2100 hydro-electric power supplies on the Volta will fall – even with the addition of a number of new hydro-electric projects.
The Volta Basin is home to the massive Akosombo Dam, which has created Lake Volta, the world’s largest man-made lake by surface area and the world’s fourth largest reservoir in terms of volume. Next year the Bui Dam, a collaboration between Ghanaian and Chinese consortia, is due to come on stream, producing 400 MW for Ghana’s power grid.
When Rose Eitmiller found a new house on Sweet Pea Lane in Dewey-Humboldt, Ariz., population 3,613, she felt at home. She was still mourning the death of a daughter whom she always called "Sweetpea," and the place seemed right to her.
The last time concentrations of the greenhouse gas carbon dioxide were as high as they are today (around 5 million years ago), big chunks of the seemingly stable East Antarctic ice sheet melted and helped raise global sea levels more than 65 feet higher than they are now, a new study suggests.
Scientists have long known that seas were higher during the Pliocene, a geological epoch that ran from 5.3 million to 2.6 million years ago. At the time, atmospheric carbon dioxide levels were similar to today's 400 parts per million (ppm).
"Overall, it was a warmer climate than today, but similar to what we expect to reach by the end of this century," Carys Cook, at the Grantham Institute for Climate Change at Imperial College London and the study's lead author, said.
The West Antarctic and Greenland ice sheets were likely completely melted at the time, she added. The fate of the East Antarctic ice sheet has been less clear, though at least some of it must have melted to fully account for the highest global sea levels predicted by some reconstructions of the ancient Earth.
Cook and her colleagues studied the chemical composition of sediments drilled from the ocean floor near East Antarctica. They identified the signature of a specific type of rock "only found in large quantities hundreds of kilometers inland from the current ice sheet edge," Cook said.
Fretwell et al. 2013Map shows the surface shape of the Antarctic continent once all of the ice has been lifted off to expose the underlying continent. Blues represent areas that lie below sea level, including the Wilkes Subglacial Basin, which in places is up to 2.8 km deep.
The signature was strongest during the warmest phases of the Pliocene. "The only way it could have been eroded is by retreating the East Antarctic ice sheet inland, which means it must have melted significantly," she explained.
Cook and colleagues suggest that much of the ice that melted was in basins that were below sea level, putting it in direct contact with the seawater. As the ocean warmed, the ice was more vulnerable to melting.
That interpretation fits with recent airborne surveys that revealed large under-ice fjords in this part of Antarctica that appeared geologically young and carved by ice, and not as a result of plate tectonics, according to Duncan Young, a geophysicist at the University of Texas at Austin, who flew some of the surveys. "This work reinforces that result," Cook explains.
The new study is also "a shot in favor" of the argument that the East Antarctic ice sheet is less stable than previously believed, "which may be significant for future sea level change estimates," said Duncan, who was not involved in the new research.
Given the similarity between the Pliocene's estimated atmospheric carbon dioxide levels and those of today, scientists consider the epoch an analog for understanding how the present-day climate will evolve.
"What the study shows is that there is a clear record of rapid(-ish) sea level response to past climate shifts," Ted Scambos, an Antarctic ice expert at the National Snow and Ice Data Center in Boulder, Co, said.
While the East Antarctic basins are covered in ice today, they might begin to melt as the oceans continue to warm, Scambos said. He noted that a mile-thick, Colorado-sized chunk of ice sloughing into the ocean would have a "big impact" on sea levels.
"And what we're seeing in other parts of Antarctica and Greenland today tells us that the transitions can be very abrupt by geologic standards," Scambos said. "They are mercifully more manageable by human standards, at least if we decide to start managing."
Here is an interim update on the uncertain future of climate change: it remains uncertain and all forecasts are, for the time being, interim. British scientists say that global warming has slowed down.
Their climate models predicted periods in which warming would slow before speeding up again, and this slowing down is within their calculated limits of uncertainty: they had not, however, expected the slowdown to happen for a decade or more.
But it is happening now.
Between 1970 and 1998, the planet warmed at an average of 0.17°C per decade because of human impact on the atmosphere in the form of fossil fuel burning, forest destruction and other human activity. Between 1998 and 2012, it warmed at an average rate of 0.04°C per decade.
This slowdown is not easily explained: greenhouse gas levels in the atmosphere have continued to rise at 3.1% per year, and are now 30% higher than at any time in the last 800,000 years, and atmospheric physicists stand by their calculations about the impact of greenhouse gases on atmospheric temperatures.
So that leaves three options. One is that some of this slowdown can be explained by variations in solar radiation during the Sun’s natural 11-year cycle.
A new report finds natural gas must peak “sooner than many policymakers currently realize is necessary—if the United States is to meet its climate goals and avoid the worst impacts of global warming.”
The report, from the Center for American Progress (where I am a senior fellow), concludes:
"There needs to be a swift transition from coal to a zero-carbon future by ensuring that the use of natural gas, particularly in the electric-power sector, peaks within the next 7 years to 17 years."
This is based on climate science, pure and simple:
"… the crux of this report is that any long-term expansion and dependence on natural gas for electricity generation is incompatible with climate-stabilization targets because it also results in carbon pollution, although less than coal. The increase in global temperature must be kept within 2 degrees Celsius above preindustrial levels, which means that the concentration of atmospheric greenhouse gas must be stabilized within 450 parts per million, or ppm, CO2 equivalent by 2050. This is the internationally recognized threshold, which was adopted in 2010 at the 16th session of the Conference of the Parties to the U.N. Framework Convention on Climate Change. Exceeding the 2 degree threshold would cause severe and frequent droughts, heat waves, floods, and storms, and lower-income households would be harmed the most, as they are less able to prepare for and recover from climate disasters."
To meet the 2C (3.6F) goal, the Obama administration set these emissions-reduction targets, relative to 2005 levels:
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