WASHINGTON — The year 2012 signalled more bad news for the state of the Earth’s climate as global land and ocean temperatures continued to rise, accelerating the decline of Arctic summer sea ice, the melting of ice sheets and glaciers, and the raising of sea levels, according to a peer-reviewed scientific report.
The report also noted an increase in the frequency and intensity of extreme storms and the continued warming of ever-deeper levels of permafrost in Canada, Alaska and Eurasia.
“You see a consistent picture, and the one we are seeing is one of a generally warmer world,” Dr. Thomas Karl, director of the U.S. National Climatic Data Center, said in a conference call with reporters.
The lead U.S. and British scientists who wrote the report, however, expressed great reluctance to explain why the data they collected shows often record or near-record increases in warming and sea level rises in 2012.
Skeptics of climate change often point out that since a record high global temperature was reached in 1998, temperatures at first decreased, then did not rise as quickly over the next 15 years despite increased greenhouse gas emissions. Scientists note that in 1998 there was a fairly intensive warming from the natural El Nino cycle, followed by a natural La Nina cooling cycle.
Karl said that over the past 50 years average global temperatures have been increasing consistently at a rate of about 1.5 C per decade.
“What we have learned is one has to take a broad look at the climate system because we recognize that there is a lot of variability in the climate system from year to year,” he said.
The report is the 23rd annual State of the Climate report compiled by 384 scientists from 52 countries and published in the Bulletin of the American Meteorological Society. The data shows that despite natural cooling trends, the planet has again warmed over the past few years. This coincides with increase amounts of greenhouse gases humans continue to pump into the atmosphere.
In 2012, global carbon dioxide levels reached 392.6 parts per million, an increase of 2.1 ppm from 2011. This is the highest level in 800,000 years, scientists say. It is well above pre-industrial levels of about 280 ppm.
“These are real signals that the world continues to get warmer,” said Dr. Kate Willett, a senior scientist at the weather office at the Hadley Center in England.
Methane levels in the atmosphere also increased, but again scientists were unable to explain why. “I can’t say precisely what is the cause of that increase in methane from 2005,” Willett said.
She added, however, that it could be explained by natural variability in climate and/or increased farming and permafrost melt. She said about 30 per cent of methane emissions come from farming and 40 per cent are natural emissions from oceans, wetlands and melting permafrost.
One of the more alarming findings is that sea levels are rising at an accelerating pace after a slight decline in 2011. They reached a record high in 2012. Most of this increase is attributed to ice-melt. The heat content of the upper 2,300 feet of the ocean remained near record high values in 2012.
Kathryn Sullivan, U.S. acting under secretary of commerce for oceans and atmosphere, warned governments need to take into account the changing climate as they plan infrastructure work into the distant future.
“Many of the planning models that are used in infrastructure planning rely on a set of assumptions that essentially count on the future being statistically a lot like the past,” she said. “Trends that we are seeing certainly in the data we have today should lead one to test the soundness of those assumptions.”
She said the high number of extreme weather events cited in the report and previous reports “caution us to be looking at a likely future where extremes and intensity of some extremes are more frequent and more intense than what we have accounted for in the past.”
The scientists said that the trend toward record-high temperatures and ice melt are the new norm.