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Offshore wind could calm hurricanes

February 26, 2014 in Climate, Coastal Threats, Energy, Extreme weather, Hurricanes, Technology, USA, Weather Systems, Wind power

FOR IMMEDIATE RELEASE

It's smaller, but the same principle applies: Wind energy is dissipated as it crosses a wind farm Image: By Michael via Wikimedia Commons

It’s smaller, but the same principle applies: Wind energy is dissipated as it crosses a wind farm
Image: By Michael via Wikimedia Commons

By Tim Radford

US scientists say that very large wind farms could not only withstand a hurricane: they would also weaken it and so protect coastal communities.

LONDON, 26 February – US engineers have thought of a new way to take the heat out of a hurricane. Fortuitously-placed offshore wind farms could make dramatic reductions in wind speeds and storm surge wave heights.

Hurricanes are capricious consequences of peculiar sea temperature and wind conditions, while wind farms are the outcome of years of thoughtful design and investment, and not an emergency response to a severe weather warning.

But, according to new research in Nature Climate Change, a giant wind farm off the coast of New Orleans in 2005 could have lowered the wind speeds of Hurricane Katrina by between 80 and 98 miles an hour, and decreased the storm surge by 79%.

Katrina was a calamitous event that caught civic, state and federal authorities off-guard, and devastated the city. But an array of 78,000 wind turbines off the coast would, according to Mark Jacobson of Stanford University, and Cristina Archer and Willett Kempton of the University of Delaware, have defused its force dramatically – and turned a lot of hurricane energy into electricity at the same time.

Wind turbines turn in the wind to generate energy. The laws of thermodynamics are inexorable, so a national grid’s gain is the wind’s loss, because wind energy is dissipated as it crosses a wind farm. One turbine literally takes the wind out of the sails of another.

Tempest models

One of the three Nature Climate Change authors, Cristina Archer, last year examined the geometry of a hypothetical wind farm to work out how to place turbines most efficiently to make the best of a gusty day, rather than have one bank of turbines turning furiously while the others barely stir.

But this same translation of wind circulation to electrical circuitry suggested another accidental consequence. Mark Jacobson and his colleagues used sophisticated computer models to test the impact of a hurricane on a wind farm, and since the US has both cruel experience and highly detailed records of hurricane events, he and his Delaware partners decided to model three notorious tempests: Superstorm Sandy, which slammed into New York in 2012 and caused $82 billion damage in three US states, Hurricane Isaac, which hit Louisiana the same year, and Hurricane Katrina in 2005.

“We found that when wind turbines are present, they slow down the outer rotation winds of a hurricane,” Professor Jacobson said. ”This feeds back to decrease wave height, which reduces movement of air toward the centre of the hurricane, increasing the central pressure, which in turn slows down the winds of the entire hurricane and dissipates it faster.”

And Cristina Archer put it more vividly: “The little turbines can fight back the beast,” she said. Her colleague Willett Kempton added: “We always think about hurricanes and wind turbines as incompatible. But we find that, in large arrays, wind turbines have some ability to protect both themselves and coastal communities from the strongest winds.”

Double benefit

The conclusions are based entirely on computer simulations. Real world tests are for the moment unlikely, chiefly because wind farms tend to have dozens or, at the most, hundreds of turbines and the hurricane experiment was based on turbines in their tens of thousands, delivering hundreds of gigawatts.

But Professor Jacobson and Dr Archer tend to think big anyway. They argued in 2012 that four million wind turbines in the world’s windiest places could generate at least half the world’s electricity needs by 2030 without interfering too greatly with global atmospheric circulation.

The tempest-taming qualities of really big wind farms would deliver an added bonus: they could offer protection to vulnerable coastal cities. The costs of wind-farming on such a scale would be huge, but then the losses to coastal cities from flooding and storm damage in a rampant climate change scenario are expected to rise to $100 trillion a year by 2100.

The three authors calculate that the net cost of such projects – after considering all the good things that could come from them – would be “less than today’s fossil fuel electricity generation net cost in these regions and less than the net cost of sea walls used solely to avoid storm damage.”

A sea wall to protect one city might cost anything from $10 billion to $29 billion, and that is all it would do: protect that city. A really big wind farm would offer protection during cyclones, typhoons or hurricanes and generate carbon-free energy all year round. – Climate News Network

Insurers given severe weather warning

June 28, 2013 in Business, Climate, Mitigation, Pollution, Public Awareness, Warming, Weather

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Financial blow: severe hurricane damage to a house in Pensacola Beach, Florida, US Image: Dave Saville/FEMA Photo Library

Financial blow: severe hurricane damage to a house in Pensacola Beach, Florida
Image: Dave Saville/FEMA Photo Library

The rise in extreme weather events driven by warming of the oceans has led analysts in the global insurance industry to issue a warning that the sector risks being hit by waves of costly claims unless it starts pressurising governments to take action on greenhouse gas emissions

By Kieran Cooke

LONDON, June 28 − The global insurance industry’s own analysts warn that it faces potentially serious financial losses unless it plays an active role in urging governments to address climate-change factors such as greenhouse gas emissions.

The Geneva Association, a leading international insurance thinktank that examines trends in the global insurance industry, has published a report this week that identifies “a significant upward trend in the insured losses caused by extreme weather events”.

It warns that changes in climate mean insurance companies have entered a new, highly uncertain era, and must adapt to what it calls a “new normal” in assessing risks and setting pricing policies. Traditional ways of assessing such risks, based solely on analysing historical data, are “increasingly failing”.

The report, Warming of the Oceans and Implications for the (Re)insurance Industry, says the world’s oceans have been warming significantly as the result of rising greenhouse gas emissions − and it is this warming that is the key driver of global extreme events.

Ocean dynamics

“Understanding the changes in ocean dynamics and the complex interactions between the ocean and the atmosphere is the key to understanding current changes in the distribution, frequency and intensity of global extreme events relevant to the insurance industry − such as tropical cyclones, flash floods or extra-tropical storms,” the report says.

The warming of the oceans means an “increased loss potential” for the insurance industry, the report says. It’s uncertain how the risk associated with the warming of the oceans and changes in climate will develop over time, but the report’s authors advocate moving from traditional data-based ways of assessing such risks to what they call predictive risk estimation methods, based on various modelling techniques.

Such forecasting techniques are by no means perfect and can often give rise to  more uncertainties − although this does not mean they are not useful or scientifically sound. “It rather reflects the limits of the scientific understanding and the ability to predict extreme events in a chaotic system,” the report says.

Increased risk

The report’s authors issue a stark warning about insurance-related problems in parts of the world that are seeing increasing levels of risk matched with growing  demands for insurance, and, at the same time, decreasing levels of self-protection. Such areas might be uninsurable, the report says. “Examples for markets with this potential are UK flood or Florida wind storm insurance.”

The only way to make sure such regions remain insurable is immediately to put in place risk-mitigation measures says the report. The insurance industry should distribute high-quality information about risk associated with climate change, and should encourage adaptation through innovative product design.

The report concludes: “These actions, alongside the support of science in tackling the major challenges in projecting the impacts of ocean warming and climate change more generally, will help the insurance industry avoid market failures and increase societal resilience.” – Climate News Network

Better air quality linked to fiercer storms

June 23, 2013 in Climate, Pollution, Science, Weather

EMBARGOED UNTIL l700 GMT, SUNDAY, 23 JUNE

Weather watch: a satellite image of an active North Atlantic hurricane season Image: NOAA/NASA/GSFC

Weather watch: a satellite image of an active North Atlantic hurricane season
Image: NOAA/NASA/GSFC

By Tim Radford

British research into storm cycles has found evidence suggesting reduced atmospheric pollution may have had the unexpected side-effect of increasing the ferocity and frequency of hurricanes

LONDON, 23 June − Scientists from Britain’s Meteorological Office have fingered a new suspect in their attempt to solve the mystery of tropical storms. It is, unexpectedly, air quality.

If North Atlantic hurricanes are more destructive or more frequent, it may be linked to lower levels of atmospheric pollution. Conversely, sulphate aerosols and other particles from factory chimneys, vehicle exhausts, domestic fires, power stations and other human economic advances may have played a role in keeping tropical storms under control, at least a little, during the 20th century.

Climate scientist Nick Dunstone and fellow-researchers at the Met Office’s Hadley Centre in Exeter, Devon, report in the Nature Geoscience journal there is at least circumstantial evidence that aerosols play a more significant role in the storm cycle than anyone had expected.

The reason it has been difficult to separate the effect is a simple one: when humans burn fossil fuels, they release greenhouse gases that slowly but inexorably warm the atmosphere, and therefore the oceans. Atmosphere and ocean are together a climate system: put more energy in, and it must go somewhere. The likely consequences, most people have thought, are extremes of wind and rain.

However, for most of the 20th century, humans released greenhouse gases and also all sorts of other waste at the same time: specifically, sulphate aerosols that, as urban smog, darkened buildings, increased the acidity of the falling rain, rotted limestone structures and condemned hundreds of thousands to bronchial illnesses and, ultimately, to early graves.

It didn’t seem possible to separate the effects – at least, not until Britain, western European nations and North America introduced increasingly strict clean air legislation.

Cloud chemistry

This started to give scientists and climate modellers a chance to tease out the different effects of the two pollutants. Aerosols are important absorbers of sunlight, and they are also important in cloud chemistry – water vapour droplets have to condense on something. But important in what way? Do clouds reflect sunlight and cool the region? Or do they build up prodigious quantities of moving water and turn into the frenzies of a tropical storm? Or, overall, do sulphates cool the atmosphere a little and counteract global warming − and, if so, under what conditions?

In fact, because a greenhouse gas such as carbon dioxide stays in the atmosphere for eight decades, while soot and sulphate aerosols stay in the atmosphere for two weeks at the most, Dunstone and colleagues were able to use historical data to help identify a pattern in storm behaviour.

Greenhouse gas emissions gathered pace in the 20th century, and the gases remained in the atmosphere. But anthropogenic aerosol releases varied.

There was a lot of smog and soot before the first world war, then a fall in emissions. Factory exhausts faltered during the great depression of the 1930s, then built up again, but fell away during the second world war, before returning everywhere – and then falling away yet again as governments and voters began to respond to filthy cities and choking smoke.

Storm records

Using climate simulations, the scientists were able to match storm records and predictions from 1860 to 2050 with recorded and predicted levels of atmospheric pollution, and identify an effect.

Through much of the 20th century, the Nature Geoscience paper suggests, aerosols actually suppressed the hurricane forces by cooling the ocean waters.  It was not possible to match specific storms with a particular level of aerosol pollution, but in general there seemed to be less frequent tropical storms during periods of greater aerosol discharge.

The finding is consistent with other recent research. Smog and other discharges in the northern hemisphere in the mid-20th century were recently linked to the parching of the Sahel and the drying-up of much of Lake Chad, along with a weakening of the Indian monsoon.

However, nobody thinks the question is settled by the Met Office findings. What actually happens in a weather system, and how often, depends on many factors. Temperatures and atmospheric pollution are certainly factors, but they are not the only ones. Dust, transported over the oceans in vast clouds, must also play a role. And humans are not the only source of aerosols: volcanoes unpredictably inject huge quantities to almost stratospheric levels.

The link is only an association: as usual, the answer is provided by climate models. There is no way to conduct a controlled, double-blind experiment with an ocean’s weather. Aerosols are implicated only by association. The researchers conclude: “Our results suggest that further progress might be accelerated by an international effort to narrow the uncertainties in aerosol impacts on climate.” – Climate News Network

 

 

 

Hurricane warning is linked to climate

May 25, 2013 in Science

EMBARGOED until 2301 GMT on Friday 24 May

The mark of Sandy: A partly collapsed crane on 1 November 2012 Image: siddman

The mark of Sandy: A partly collapsed crane on 1 November 2012
Image: siddman

By Alex Kirby

One of the factors which has prompted US scientists to warn of intensified hurricane activity in the Atlantic this year is warmer water temperatures, linking storm frequency with climate change.

LONDON, 25 May – US scientists have warned Americans that they can expect more and perhaps fiercer hurricanes than usual from the Atlantic Ocean this year.

The Climate Prediction Center at the National Oceanic and Atmospheric Administration, NOAA, is forecasting ”an active or extremely active season” for hurricanes in 2013.

It says several climatic factors are expected to combine this year to cause the unusually high level of hurricane activity. One of these is the higher than usual sea temperatures.

For the six-month hurricane season, which begins on 1 June, NOAA’s Atlantic Hurricane Season Outlook says there is a 70% likelihood of 13 to 20 named storms, which have winds of 39 mph or higher.

Of these storms, NOAA says, 7 to 11 could become hurricanes, with winds of 74 mph or higher, including 3 to 6 major hurricanes, where wind speeds will reach 111 mph or more.

NOAA says: “These ranges are well above the seasonal average of 12 named storms, 6 hurricanes and 3 major hurricanes.”

Dr Kathryn Sullivan, NOAA’s acting administrator, said: “As we saw first-hand with [2012's Superstorm] Sandy, it’s important to remember that tropical storm and hurricane impacts are not limited to the coastline. Strong winds, torrential rain, flooding, and tornadoes often threaten inland areas far from where the storm first makes landfall.”

NOAA says three “climate factors that strongly control Atlantic hurricane activity” are expected to combine to produce an active or extremely active 2013 season.

One of these is the continuation of an atmospheric climate pattern, which includes a strong west African monsoon, that is responsible for the continuing era of high activity for Atlantic hurricanes dating from 1995.

More oceanic heat

 

The second factor which NOAA identifies is the warmer than average water temperatures being recorded in the tropical Atlantic Ocean and Caribbean Sea. This may have a significance beyond the hurricane forecast itself.

One suggested explanation for the slight slowdown in global warming over the last decade is that extra heat is going, not into the atmosphere, but into the oceans, and the warming to which NOAA refers appears to be consistent with this.

And to reinforce the atmospheric pattern and role of the oceans, NOAA says, El Niño (the periodic disruption of weather patterns in the Pacific) is not expected to develop and suppress the formation of hurricanes in 2013.

By contrast, NOAA is predicting that both the Eastern and the Central Pacific basins will have below-normal hurricane seasons this year.

NOAA’s seasonal hurricane outlook does not forecast where an individual hurricane is likely to make landfall, nor does it predict how many storms will hit land.

Among other improvements this year, NOAA plans in July to commission a new supercomputer which will run an upgraded Hurricane Weather Research and Forecasting (HWRF) model providing significantly better depictions of storm structure and improved storm intensity forecast guidance.

It will also transmit radar data in real time from its aircraft to help forecasters to produce better analyses of rapidly evolving storm conditions, a development which could improve the HWRF model forecasts by 10 to 15%.

NOAA will issue an updated outlook for the Atlantic hurricane season in early August, just before the historical peak of the season. – Climate News Network