Trade winds draw ‘missing’ warmth to deep ocean

Trade winds draw 'missing' warmth to deep ocean

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Contrary to some reports, global warming hasn’t stopped or slowed at all, new research suggests. The trade winds have simply carried the heat into the Pacific Ocean – temporarily.

LONDON, 10 February – Australian and US scientists think they know where a lot of global warming has been concentrated: it has been tucked away below the surface waters of the western Pacific Ocean. And the agency that took the heat out of the atmosphere and transferred it into a liquid form could have been the equatorial trade winds.

Matthew England from the Australian Centre of Excellence for Climate System Science and colleagues report in Nature Climate Change that a dramatic acceleration in the winds has drawn heat from the atmosphere and transferred it to the ocean: cooler waters have risen to the surface to mask the transaction.

Climate sceptics – and some climate scientists – talk about a slowdown, or a pause, or a hiatus in global warming. In fact, temperatures have gone on rising and 13 of the 14 warmest years ever recorded have all occurred since 2000. But the rate of rise in global average temperatures since 2000 has not been as fast as the rate during the 1980s and 1990s.

Since greenhouse gas levels have continued to rise, and since scientists are sure of their atmospheric physics, then there was some “missing heat” to be accounted for.

Researchers have variously suggested that a puzzling increase in deep ocean temperatures could be one explanation or that perhaps the unevenness of temperature measurements around the planet might be another. But both suggestions were hypotheses: nobody had an answer that could be tested by any kind of experiment.

Slower rate

Professor England and colleagues worked with observed winds, surface air temperatures, and a set of ocean climate models to calculate what may have happened.

The global warming story has always been one of fits and starts: a warming that ought to have been observed 70 years ago stalled between 1940 and 1970, and when it resumed, did so in fits and starts. The overall trend continued upward, but the rate of rise slowed noticeably during the last decade.

Ocean circulation loops are driven by winds, and speed up as the winds intensify. Cool waters well up, warm waters descend. And intensify is just what the trade winds have done. They began strengthening during the 1990s, a process which continues today. Once the researchers added the trade winds to their calculations, the global average temperatures looked very like the observations during the hiatus.

They also found that four-fifths of the surface temperature cooling occurred after 2000, which confirmed that wind acceleration was the key contributor.

“Scientists have long suspected that extra ocean heat uptake has slowed the rise of global average temperatures, but the mechanism behind the hiatus remained unclear”, said Professor England.

Rapid rise on the way

“But the heat uptake is by no means permanent: when the trade wind strength returns to normal – as it inevitably will – our research suggests heat will quickly accumulate in the atmosphere. So global temperatures look set to rise rapidly out of the hiatus, returning to the levels projected within as little as a decade.”

The same mechanism could explain the slowdown between 1940 and 1970. In 1938, the British scientist G S Callendar argued that rising carbon dioxide levels should mean global warming but the evidence proved elusive, perhaps because the trade winds accelerated during those decades.

Richard Allan, professor of climate science at the University of Reading in the UK, said the current slowdown was only a temporary reprieve.

“Measurements from satellites and ocean buoys show that the planet is absorbing more heat than it is radiating out to space and the heat is building up in the oceans.

“This new research suggests that when the trade winds weaken again, the planet can expect rapid warming of the surface to resume, as greenhouse gas concentrations continue to rise.” – Climate News Network

There’s no warming standstill says WMO

There's no warming standstill says WMO

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The head of the World Meteorological Organization tells Climate News Network there is no standstill in global warming, which is on course to continue for generations to come.

LONDON, 5 February – The planet is continuing to warm, with implications for generations ahead, and temperatures are set to rise far into the future, the World Meteorological Organization (WMO) reports.

It says 2013 was among the ten warmest years since modern records began in 1850, equalling 2007 as the sixth warmest year, with a global land and ocean surface temperature 0.50°C above the 1961–1990 average and 0.03°C higher than the most recent 2001–2010 average.

Thirteen of the 14 warmest years on record have all occurred in this century. The warmest years on record are 2010 and 2005, with global temperatures about 0.55 °C above the long-term average, followed by 1998, which also had an exceptionally strong El Niño event.

El Niño events (which intensify warming) and cooling La Niñas are major drivers of natural climate variability. Neither occurred during 2013, which was warmer than 2011 or 2012, when La Niña exerted its cooling influence. 2013 was among the four warmest neutral years recorded, when neither El Niño nor La Niña affected temperatures.

“The global temperature for the year 2013 is consistent with the long-term warming trend”, said WMO Secretary-General Michel Jarraud. “The rate of warming is not uniform but the underlying trend is undeniable. Given the record amounts of greenhouse gases in our atmosphere, global temperatures will continue to rise for generations to come.

“Which standstill? The coldest year since 2001 is warmer than any year before 1998″

“Our action – or inaction – to curb emissions of carbon dioxide and other heat-trapping gases will shape the state of our planet for our children, grandchildren and great-grandchildren”, Mr Jarraud said.

Asked by Climate News Network how WMO regarded claims by some critics that there has been a “global warming standstill since 1997″, Mr Jarraud said: “Which standstill? The coldest year since 2001 is warmer than any year before 1998.

“Each decade is warmer than the previous one. There is global variability from year to year. You have to look at the longer period. If you do that, then the message is beyond any doubt…Despite the fact that there was no El Niño in 2013, it was still the sixth warmest year. This is significant.”

The WMO says surface temperature is just part of a much wider picture of climate change. “More than 90% of the excess heat being caused by human activities is being absorbed by the ocean“, it says.

It has released the temperature data in advance of its full Statement on the Status of the Climate in 2013, to be published in March. This will give more details of regional temperatures and other indicators.

Consistent findings

In contrast with 2012, when the US in particular experienced record high annual temperatures, the warmth in 2013 was most extreme in Australia, which had its hottest year on record.

WMO’s global temperature analysis is based mainly on three independent and complementary datasets. One is maintained by two UK centres, the Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia. The other two are based in the US: NOAA’s National Climatic Data Center, and the Goddard Institute for Space Studies (GISS), operated by NASA.

Each dataset uses slightly different methods of calculation and so each gave 2013 a different temperature ranking, but they were consistent on the year-by-year changes and the longer warming trends globally.

WMO also uses reanalysis-based data from the European Centre for Medium-Range Weather Forecasts (ECMWF), which showed annual global land and ocean temperature to be the fourth highest on record. – Climate News Network