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Dr. Jane Goodall

Global Warming Caused By Natural Variations

| Modified 23 Feb, 2016 | Views 1423

Scientists have had trouble explaining why satellite data shows that average global temperatures have been virtually flat for more than 18 years.

Former UN Lead Author: Global Warming Caused By ‘Natural Variations’ In Climate

Global temperature change observed over the last hundred years or so is well within the natural variability of the last 8,000 years, according to a new paper by a former Intergovernmental Panel On Climate Change (IPCC) lead author.

Dr. Philip Lloyd, a South Africa-based physicist and climate researcher, examined ice core-based temperature data going back 8,000 years to gain perspective on the magnitude of global temperature changes over the 20th Century.

“This suggests that while some portion of the temperature change observed in the 20th century was probably caused by greenhouse gases, there is a strong likelihood that the major portion was due to natural variations,” Lloyd wrote in his study.

But Lloyd’s study hits at a larger debate within climate science: how much warming is attributable to mankind or nature. Clearly, Lloyd and the IPCC he once contributed to now represent different ends of the spectrum.

At the time, Ronald Bailey, a science write for Reason magazine, wrote that there has still not been enough observed warming to meet the IPCC’s standard of “enhanced warming” — that is, warming above natural levels.

“The magnitude of natural climate variability over the past 1000 years and even the past 100 years is hotly debated,” Curry added. “Personally, I think the role of natural climate variability has been substantially underestimated in our interpretation of recent climate change.”

“I would not pin anything on what was said by IPCC in 1990,” Dr. Kevin Trenberth, a climate scientist with the National Center for Atmospheric Research, told TheDCNF in April. “In the reports since then there have been thorough evaluations of past IPCC projections and whether they were out of line.”

Human influence on the climate may have been observable in the 1970s, but scientists have had trouble explaining why satellite data shows that average global temperatures have been virtually flat for more than 18 years. Satellites measure the troposphere — the lowest few miles of the atmosphere — in contrast, to surface temperature measurements, which most climate bodies rely on for estimates of global average temperature average.

But even surface temperature data showed a hiatus in warming for about 15 years or so. Scientists have offered up dozens of explanations for why global temperatures have been flat since the late since the late 1990s.

“What is evident now is that the signal of global warming emerged from the noise of natural variability about the mid 1970s,” Trenberth added. “There are fluctuations in global mean temperatures: from year to year with El Niños, etc., and from decade to decade, so that trends reflecting global warming need to be taken over at least 20 years.”


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