ENVIRONMENT: by Peter WestmoreNews Weekly
Global warming, the latest evidence
, May 28, 2011
Despite continued claims of uncontrolled global warming, the latest data show that average surface temperatures, Arctic sea ice levels and seawater temperatures around the world are within the range which has been observed for many years.
The average figures are important because local variations can lead people to generalise from their own experience to reach incorrect conclusions.
For example, the northern hemisphere has experienced three successive severe winters, although average global temperatures have not shown this trend.
And the British Met Office, a strong supporter of the Intergovernmental Panel on Climate Change (IPCC), recently stated that English temperatures in April have been the highest on record. However, parts of central Europe, including Poland, have experienced unseasonal snows at the same time.
A related problem is that measurements of temperature around the world depend on where weather stations are located. With increased urbanisation and the closure of weather stations in many rural areas, and the scarcity of stations over the oceans which cover more than three-quarters of the earth’s surface, the data can easily be skewed to produce apparently higher temperatures.
Since 1979, American satellites have carried instruments which read the naturally-occurring microwave emissions from oxygen in the atmosphere. These emissions are temperature-related, and can also be isolated to different levels of the atmosphere, enabling, for the first time, average temperatures for the earth to be calculated.
Two American meteorologists, John Christy and Roy Spencer, update these global temperature data-sets obtained from the satellites, and they are regularly posted on the internet at www.drroyspencer.com
The latest figures show that average atmospheric temperatures are just above the average for the past 30 years, having risen from just below the average, as shown in the accompanying Chart 1.
Another indicator of global warming, we are told, is the melting of the Arctic sea ice. A recent report claimed that the Arctic ice sheet was melting at an alarming rate.
The fact is that every year, the Arctic ice sheet undergoes a massive degree of freezing in winter, and thawing in summer. On average, the Arctic ice sheet covers the entire Arctic Ocean in winter and extends to about 14 million square km, and melts in summer to around 5 million square km, due to both increased solar radiation and warm waters flowing into the Arctic.
The University of Bremen’s web site shows that current sea ice levels are comparable with those of recent years (Chart 2).
There is nothing new in this. Since the 16th century, Britain tried to exploit the melting of the Arctic sea in its quest for the fabled North-West Passage, north of Canada, to find a shorter route to Asia than going around Cape Horn in South America, or the Cape of Good Hope in South Africa.
The most famous expedition to find the North-West Passage was led by a former Governor of Tasmania, Sir John Franklin, in 1845. The Franklin expedition, containing two well-equipped ships, ended in disaster when the ships became locked in ice, and every man in the expedition perished in horrific circumstances over subsequent years, despite frantic efforts to discover where they had been lost.
While there has been a small decline in measured Arctic sea ice over the past 40 years, the Antarctic ice mass has risen slightly, so the overall quantity of sea ice has remained almost constant over the same period.
Sea surface temperature charts, produced weekly by the US National Oceanic and Atmosphere Administration (NOAA), show little overall difference from the average temperatures measured from 1971 to 2000; and global mean sea levels, charted by the University of Colorado (Chart 3), are estimated to have risen about 5 cm over the past 18 years, far less than the normal tidal difference caused by the moon and the sun, which in many parts of the world is measured in metres, and by the impact of ocean waves.
Despite this, the UN General Assembly in 2008 made the alarmist declaration that there would be between 50 and 200 million climate refugees by 2010. Of course, the declaration has been proved false — but not before hundreds of millions of dollars have been spent in a futile attempt to control the earth’s climate.
Chart 1: Global lower atmosphere temperatures (1979-2011)
Chart 2: Arctic sea ice extent (2003-2011)
Chart 3: Mean sea level since 1992