Research & Commentary: Temperature Observations

Published October 14, 2013

One of the central premises behind the concern that manmade greenhouse gas emissions may be causing dangerous global warming is that global temperatures have increased over the last century in concert with human carbon-dioxide production. This trend should therefore be seen in the last 15 years as more people embraced industrialization around the world. A report from the Nongovernmental International Panel on Climate Change (NIPCC), an independent group of some 50 scientists from 15 countries, titled Climate Change Reconsidered II: Physical Science (CCR-II), summarizes a large body of research challenging these claims and asserts warming patterns over the last century have coincided with normal historical climate patterns.

CCR-II reports there has been little or no connection historically between carbon dioxide (CO2) levels and global temperature. During the Holocene era, global temperatures were as warm as, if not warmer than, today, despite approximately 30 percent lower atmospheric CO2 levels. Similarly, Earth experienced a warming period during the Middle Ages (usually referred to as the Medieval Warm Period) despite far lower CO2 levels than today’s.

CCR-II demonstrates the Intergovernmental Panel on Climate Change (IPCC) overestimates the rise in global temperatures over the last few decades because of a number of measurement errors. For example, the IPCC fails to properly account for the effects of land alteration, such as urbanization, on surface temperatures and temperature measurements. Even the temperature effects of small towns can far outweigh the effects of greenhouse gases. The IPCC also failed to produce compelling scientific arguments connecting CO2 levels with icecap coverage.

Concern over manmade greenhouse gas emissions has been the impetus for many destructive public policies, including renewable portfolio standards, alternative energy subsidies, and high gasoline taxes. Yet, despite ever-increasing manmade CO2 emissions, the global temperature has not risen for at least the past 15 years. CCR-II‘s findings demonstrate global temperatures have little or no connection to manmade CO2 emissions. This suggests governments should not hinder energy production, the lifeblood of the global economy, over temperature concerns.

The above introduction is based on text from Climate Change Reconsidered II: Physical Science and its Summary for Policymakers, which were published by The Heartland Institute for the Nongovernmental International Panel on Climate Change (NIPCC).

The following documents provide additional information about global temperature trends.


Chapter 4 of Climate Change Reconsidered II
In Chapter Four of Climate Change Reconsidered II: Physical Science, Sherwood Idso, Craig Idso, and Roy Spencer present evidence showing it’s extremely likely natural variability is responsible for late-twentieth century warming and the cessation of warming since 1998. The modern rise of CO2 and other atmospheric greenhouse gases has had little, if any, measurable effect on the global climate.

Summary for Policymakers of Climate Change Reconsidered II
The IPCC claims to know, apparently with rising certainty over time, that “most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations” (IPCC AR4 SPM, p. 10). This Summary for Policymakers summarizes and explains Climate Change Reconsidered II, a major scientific report that thoroughly refutes the IPCC’s claim. 

Global Warming Hiatus Puts Climate Change Scientists on the Spot,0,791164.story
In the September 22, 2013 edition of the Los Angeles Times, Monte Morin reports on the predicament faced by alarmist scientists who can’t explain current temperature trends, which have run counter to the IPCC’s models. In Stockholm, IPCC scientists were unable to reach consensus on what could be causing the discrepancy. Theories about why temperatures have not increased include a lack of sunspot activity, low levels of water vapor in the atmosphere, and the phenomenon of heat being trapped under the ocean’s surface. 

Global Warming? No, Actually We’re Cooling, Claim Scientists
Haley Dixon examines recent data for the Telegraph on September 8, 2013, which show a 60 percent increase in polar ice coverage over the previous year. The data are the latest in a string of reports that directly contradict the IPCC’s global warming models. Despite being 95% confident in dangerous climate change, the IPCC proposed 1,500 amendments to its 2007 climate change report. Dixon reports many scientists still believe in dangerous climate change despite a freeze in global temperatures since 1997, which they attribute to a “pause” in the general warming trend. 

Early 20th Century Global Warming
In this 2011 paper published in the Eos Transactions American Geophysical Union, Dr. Fred Singer details a serious error in the IPCC’s climate analysis: an arbitrary focus of attention on the years 1940–1990. The IPCC misreports the temperature trends of the period, and these 50 years have no special significance. Wider time ranges actually show stable if not decreasing temperature trends. The IPCC’s conclusions are based on inaccurate, cherry-picked data. 

Urbanization Effects upon the Air Temperature in Mexicali, B.C., México
This 2009 paper published in Garcia Cueto demonstrates the effects of urbanization on surface air temperatures. Fifty years’ worth of temperature data show vastly different trends between Mexicali City and its rural surroundings, with the temperature differentiation reaching as high as 5.7°C during the winter. The researchers conclude urban population centers create “urban heat island” effects that increase measured temperatures regardless of climate patterns. 

Models Fail: Greenland and Iceland Land Surface Air Temperature Anomalies
Bob Tisdale examines some recent climate temperature model failures in this July 6, 2013 article for He notes alarmist climate change advocates often point to faster-than-expected warming in certain geographic areas as evidence for the theory, even though such anomalies further discredit their models by deviating from the models’ predictions. Naturally, as some areas see more warming than expected, plenty of regions experience less warming or even cooling, due to natural climate variability. Tisdale also notes the timeframes on which models are based are crucially important—alarmist climate change advocates often cherry-pick timeframes and omit broader data that contradicts their claims. 

Whatever Happened to Climate Change
Writing for the September 22, 2013 Independent, Paul Valley attributes the rising skepticism toward climate change alarmism to increased confusion over the trending of global temperatures. Polls show support for climate change alarm is falling in the UK as climate models have contradicted the actual temperature changes over the last decade. Valley notes climate change is a far more complicated process than is often presented to the public by leading climate experts. Unfortunately, the media have generally presented an equally unsophisticated view and lack an understanding of long-term climate trends.


Nothing in this Research & Commentary is intended to influence the passage of legislation, and it does not necessarily represent the views of The Heartland Institute. For further information on this and other topics, visit the Environment & Climate News Web site at, The Heartland Institute’s Web site at, and PolicyBot, Heartland’s free online research database, at

If you have any questions about this issue or The Heartland Institute, or would like a scientist to testify in your state, contact Heartland Institute Policy Analyst Taylor Smith at [email protected] or 312/377-4000.