. The heated debate between climate deniers and those who think global warming is real – who claim that global warming was a result of human activity and that we’re the reason – is set to heat up again. Scientists have confirmed that global warming has indeed slowed down. When first observed several years back, a deceleration of the rise in global temperatures was called a “hiatus” (pause). After a series of congressional hearings and many skeptical blogs, the global warming “hiatus” was finally curbed by 2015.. All that is coming back? The graph below shows that there has been a slowdown in the rise of temperatures to 2010.. While the black line is a projection of climate models’ temperature, the red line represents actual temperatures. Recent warming has accelerated, setting new historical records for 2014 as well as 2015.. Image: Nature Climate Change. The hiatus was not an artifact. Climate change deniers insist that this slowdown was not a coincidence. They claim that the global warming phenomenon was temporary and that the earth stopped heating in 1998.. In June 2015,, Science published a study that concluded the hiatus is a temporary phenomenon which fades once biases in temperature data have been corrected. An international team of distinguished scientists representing Australia, Canada, Japan, the UK and other countries is disputing this claim. In Nature Climate Change, they wrote that the slowdown had occurred even though these biases were corrected. John Fyfe (lead author), is a climate modeler with the Canadian Centre for Climate Modelling and Analysis, Victoria, British Columbia. He said that there was ‘a mismatch’ between the models and the data. It’s not something we can ignore. 2014 saw a record-breaking year of warmth. Image: ncdc.noaa.gov. Dr. Fyfe calls it a “slowdown” and not a “hiatus”. It does not undermine climate change theory (global heating), he emphasizes. Partly, the controversy centers around temperature trends and patterns statistics. Study that challenged the existence and trend of the slowdown corrects known biases in surface temperature records maintained by NOAA (U.S. National Oceanic and Atmospheric Administration). These include temperature differences between buoys and ships. The record-warming year last year was included in the study. This increased the recorded warming. Additionally, the researchers extended the record to 2014,. Last year was also a record year for average temperature. Thomas Karl (director of NOAA’s National Centers for Environmental Information) calculated that global warming rate from 1950 up to 1999 was 0. 113 degrees Celsius per decade, similar to the 0. 116degC per decade calculated for the 2000 to 2014 period. Dr. Karl stated that this means that the 2013 assessment by the Intergovernmental Panel on Climate Change, which showed that global warming has slowed down, was not valid. According to Dr. Fyfe’s latest study, his colleagues claim that Dr. Karl was biased because of the period in which temperatures were relatively flat. These periods were from the 1950s through the early 1970s. The emissions of industrial pollutants such as sulphate (USA sulfate), aerosols, kept the Earth cooler by reflecting sunlight back into the space. The Earth’s temperature increased significantly after 2000 Dr. Fyfe, along with his team calculated that the Earth had warmed to 0. 170degC per decade from 1972 to 2001, which is considerably more than the 0. 113degC per decade he and his team calculated for 2000 to 2014. His approach, Dr. Fyfe claims is superior because it considers the effects of decadal temperatures trends. Studies have shown that climate models underestimated the warming effect from solar radiation, and overestimated its cooling effects at the start of the century. Scientists are also studying the variability of the Pacific Ocean. This includes a measurement of ocean surface temperatures (Pacific Decadal Oscillation). These factors can have a significant impact on the climate and may mask long-term warming trends. Writing in Nature News, Jeff Tollefson quoted Susan Solomon, a climatologist at MIT, who said that Dr. Fyfe’s framework helps put 21st-century trends into perspective, and clearly shows that the rate of warming decelerated at a time when greenhouse-gas emissions were increasing dramatically. Internationally recognized leader in atmospheric science, Dr. Solomon said that it was important to explain this. Scientists are interested in every curve and bump. Dr. Solomon is internationally recognized as a leader in atmospheric science. Dr. Karl stated that the ultimate goal to uncover the warming caused by persistent greenhouse forcing is lost. It is simply not possible to gain insight on that underlying trend from short, segmented 10- to 20-year periods.” Director of NASA’s Goddard Institute for Space Studies in New York, Gavin Schmidt, says he is fed up with the entire discussion, which he says comes down to academic bickering and pointless arguments on definitions. The long-term trend in warming persists Schmidt says that there’s no evidence to support a shift in this trend. This scientific dispute could spread to the skeptical blogosphere. But that doesn’t mean we should ignore the slowdown, according to Michael Mann (a co-author and climatologist at Pennsylvania State University). Scientific American quotes Dr. Mann saying that “As scientists we have to go where the evidence leads us. We can’t let our concerns about climate contrarians or how they might misrepresent the work we did to determine what we publish.” The slowdown at the start of the century was over, and 2014 recorded record heat. Dr. Mann stated: “So, we have every reason for believing that the warming and its detrimental effects will continue to increase if we don’t drastically reduce our emissions.” Nature Climate Change 6, 224-228. 24 February, 2016. DOI: 10.1038/nclimate2938. Video – 10 signs that global warming is real
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