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 Intergovernmental Panel On Climate Change (IPCC) lead author Dr. Philip Lloyd.

 Dr. Philip Lloyd is a South Africa-based physicist and climate researcher, Dr. Lloyd 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.

What Lloyd found was that the standard deviation of the temperature over the last 8,000 years was about 0.98 degrees Celsius– higher than the 0.85 degrees climate scientists say the world has warmed over the last 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.

The United Nations’ IPCC claims there’s been 0.85 degrees Celsius of warming since the late 1800s, and concludes that most of this warming is due to human activities– mainly, the burning of fossil fuels and changes in land use. The IPCC says that “more than half of the observed increase in global average surface temperature from 1951 to 2010” have been caused by human activity.

 If Lloyd’s results hold, the IPCC may have to revise how much warming it attributes to mankind. In any case, the IPCC’s estimate of man-made and natural warming (0.85 degrees) is still below the standard deviation for the last 8,000, according to Lloyd’s results. This means that warming is not very significant within the context of the Earth’s recent climate history.

Lloyd arrived at his conclusion after the “differences in temperatures between all records which are approximately a century apart were determined, after any trends in the data had been removed.” Lloyd noted the “differences were close to normally distributed.”

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.

 “The key challenge in understanding climate change is to assess the natural climate variability,” Dr. Judith Curry, a climate scientist at Georgia Tech, told The Daily Caller News Foundation in April.

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.

 In his article, Bailey noted that there has not been enough temperature rise since the IPCC set its benchmark for “enhanced warming” in 1990. Curry noted that there was a big jump in temperature between 1993 and 1998, but that was basically because of the latter year’s El Niño.

 “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.”

But not all scientists agree with Bailey’s article, and some argue that signs of human influence on the Earth’s climate were evident in the 1970s. Indeed, by 1995 the IPCC stated that the “balance of evidence suggests a discernible human influence on global climate.” The international body has only made stronger statement on man’s climatic influence ever since.

“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 1990s. The most prominent explanation is that oceans have been absorbing most of the “heat” from increased greenhouse gas emissions, meaning surface temperatures show less warming than they otherwise would.

 “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.”




Climate Change

Climate change is a significant time variation in weather patterns occurring over periods ranging from decades to millions of years. Climate change may refer to a change in average weather conditions, or in the time variation of weather around longer-term average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors such as biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcanic eruptions. Certain human activities have also been identified as significant causes of recent climate change, often referred to as global warming.

Scientists actively work to understand past and future climate by using observations and theoretical models. A climate record — extending deep into the Earth's past — has been assembled, and continues to be built up, based on geological evidence from borehole temperature profiles, cores removed from deep accumulations of ice, floral and faunal records, glacial and periglacial processes, stable-isotope and other analyses of sediment layers, and records of past sea levels. More recent data are provided by the instrumental record. General circulation models, based on the physical sciences, are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.




Global Warming

Global warming is the observed century-scale rise in the average temperature of Earth's climate system. Since 1971, 90% of the increased energy has been stored in the oceans, mostly in the 0 to 700m region. Despite the oceans' dominant role in energy storage, the term "global warming" is also used to refer to increases in average temperature of the air and sea at Earth's surface. Since the early 20th century, the global air and sea surface temperature has increased about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980. Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850

Scientific understanding of the cause of global warming has been increasing. In its fourth assessment (AR4 2007) of the relevant scientific literature, the Intergovernmental Panel on Climate Change (IPCC) reported that scientists were more than 90% certain that most of global warming was being caused by increasing concentrations of greenhouse gases produced by human activities. In 2010 that finding was recognized by the national science academies of all major industrialized nations

Affirming these findings in 2013, the IPCC stated that the largest driver of global warming is carbon dioxide (CO2) emissions from fossil fuel combustion, cement production, and land use changes such as deforestation. Its 2013 report states:

Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely (95-100%) that human influence has been the dominant cause of the observed warming since the mid-20th century. - IPCC AR5 WG1 Summary for Policymakers

Climate model projections were summarized in the 2013 Fifth Assessment Report (AR5) by the Intergovernmental Panel on Climate Change (IPCC). They indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7 °C (0.5 to 3.1 °F) for their lowest emissions scenario using stringent mitigation and 2.6 to 4.8 °C (4.7 to 8.6 °F) for their highest. The ranges of these estimates arise from the use of models with differing sensitivity to greenhouse gas concentrations.

Future climate change and associated impacts will vary from region to region around the globe. The effects of an increase in global temperature include a rise in sea levels and a change in the amount and pattern of precipitation, as well as a probable expansion of subtropical deserts. Warming is expected to be strongest in the Arctic, with the continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent extreme weather events including heat waves, droughts and heavy rainfall; ocean acidification; and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the loss of habitat from inundation.

Proposed policy responses to global warming include mitigation by emissions reduction, adaptation to its effects, building systems resilient to its effects, and possible future climate engineering. Most countries are parties to the United Nations Framework Convention on Climate Change (UNFCCC), whose ultimate objective is to prevent dangerous anthropogenic (i.e., human-induced) climate change. Parties to the UNFCCC have adopted a range of policies designed to reduce greenhouse gas emissions and to assist in adaptation to global warming. Parties to the UNFCCC have agreed that deep cuts in emissions are required, and that future global warming should be limited to below 2.0 °C (3.6 °F) relative to the pre-industrial level. Reports published in 2011 by the United Nations Environment Programmers and the International Energy Agency suggest that efforts as of the early 21st century to reduce emissions may be inadequate to meet the UNFCCC's 2 °C target.

Emissions of greenhouse gases grew 2.2% per year between 2000 and 2010, compared with 1.3% per year from 1970 to 2000.


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