Archive for ‘Climate change’

November 19, 2011

Climate panel says prepare for weird weather

This certainly won’t change many skeptics’ minds… but for everyone else it further emphasizes the dangers (as if more were needed).

What mainly motivates the skeptics, it seems, is fears about the costs of reducing emissions of greenhouse gases, especially CO2. That will certainly entail costs, but even those are not easy to predict. Ironically, and unfortunately for the companies involved, the cost of photovoltaic energy has been plummeting, as the required materials (especially polysilicon) have become much cheaper. This, along with limitations on demand due to economic turbulence (especially in Europe), has put a number of solar companies out of business. But the trend is clear: photovoltaic energy, and other forms of solar energy, just keep getting more affordable. The exact opposite is true for fossil fuels, even without taking account of global warming and other externalities.

It’s not so hard to predict that there will be significant effects of accelerated global warming, but it’s harder to predict the timing and magnitude of the effects and their costs. Some costly effects seem pretty likely, such as extended periods of drought in many places, loss of habitable land, due to sea level rise, where many millions of people now live, poorer health and more deaths due to higher temperatures and severe shortages of food and potable water. And so forth.

And then there are the wildcards associated with extreme weather – severe flooding, more frequent and more intense hurricanes and tornadoes, forest fires resulting from prolonged heat waves.

Some of these extremes appear to be nearly certain, while others remain unpredictable possibilities. But even the possibilities, and their costs, need to be accounted for in terms of increased statistical expectation. You don’t know how much you’ll lose during a weekend at the Las Vegas casinos, but if you look at the odds (and the profits the casinos make), you can calculate the expected loss.

Climate panel says prepare for weird weather

Extreme weather, such as the 2010 Russian heat wave or the drought in the horn of Africa, will become more frequent and severe as the planet warms, the Intergovernmental Panel on Climate Change (IPCC) warns in a report released today. Some areas could become “increasingly marginal as places to live in”, the report concludes.

It is “virtually certain” — meaning 99–100% probability in IPCC terminology — that the twenty-first century will see an increase in the frequency and magnitude of warm temperature extremes and a decrease in cold extremes.

It is much less clear, however, how climate change will affect rainfall, flood risk and storminess.

And these weather events aren’t independent things either. Extremes in one part of the global weather system can lead to extremes in other parts. For example, the 2010 Russian heat wave and the severe flooding in Pakistan. (References: here, here)

It’s unfortunate that people don’t have too much trouble understanding the need to prepare for unpredictable events like earthquakes or even asteroid impacts – yet there’s so much reluctance to do anything about far more predictable outcomes associated with extreme weather.

Further reading:

Science panel: Get ready for extreme weather

IPCC Report: Global Warming—and Changing Population—Will Worsen the Toll of Extreme Weather

U.N. Panel Finds Climate Change Behind Some Extreme Weather Events

IPCC says it again – more confidently – expect extreme weather more often

September 21, 2011

Deep Oceans May Mask Global Warming for Years at a Time

Very few processes in nature proceed uniformly in one direction when examined at increasingly small time intervals. One would not expect rising temperatures every day from February through July at a place in the northern hemisphere. But on average, if measured over a number of years, one certainly would. On a global scale, there will be fluctuations lasting as much as a decade, but the long-term trend remains.

Deep Oceans May Mask Global Warming for Years at a Time – US National Science Foundation

Earth’s deep oceans may absorb enough heat at times to flatten the rate of global warming for periods of as long as a decade–even in the midst of longer-term warming. This according to a new analysis led by scientists at the National Center for Atmospheric Research (NCAR).

The study, based on computer simulations of global climate, points to ocean layers deeper than 1,000 feet as the main location of the “missing heat” during periods such as the past decade when global air temperatures showed little trend.

The findings also suggest that several more intervals like this can be expected over the next century, even as the trend toward overall warming continues.

Further reading:

Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods

September 13, 2011

Arctic sea ice drops to record low

Sea ice melting keeps growing….

Arctic sea ice drops to record low – Nature News Blog

Arctic sea ice extent last week dropped to a new record minimum. At 4.24 million square kilometres, sea ice cover on 8 September was 27,000 sq km below the previous record low, observed in 2007.

Maps produced by scientists at the University of Bremen in Germany — on the basis of high-resolution microwave data from a sensor on board NASA’s Aqua satellite — first showed on 5 September that ice extent was lower than on the same date in 2007.

Further reading:

Summer Arctic melt among worst ever

Arctic Sea Ice Hits Record Low, According to One Measure

September 9, 2011

Researchers predict extreme summertime temperatures to become a regular occurrence

Was it unusually hot this summer where you live? If so, expect that to become the rule rather than the exception if global warming results in even a 2° C rise in the average temperature.

Researchers predict extreme summertime temperatures to become a regular occurrence

Anderson’s research indicates that if the 2°C increase were to come to pass 70-80% of the land surface will experience summertime temperature values that exceed observed historical extremes (equivalent to the top 5% of summertime temperatures experienced during the second half of the 20th century) in at least half of all years. In other words, even if an increase in the global mean temperature is limited to 2°C, current historical extreme values will still effectively become the norm for 70-80% of the earth’s land surface.