Question 2. Is the Earth Warming, Cooling or Stable

A. Definition of Global Warming or Cooling

Air temperatures change by the minute and are effected by a number of factors, including location, altitude, etc.  If the high yesterday was 75°F and today it is 85°F, it cannot be inferred that the world temperature has increased 10°F.  The temperature change, or “anomaly,” is the difference between the highest and lowest measurements for the day compared to a year ago.  The temperature outside your house or the highest or lowest temperatures on record, as reported by the media, are meaningless in relation to “climate change,” i.e., whether the surface of the earth is warming or cooling in relation to a selected period.

B. Reported Global Temperature Anomaly (change) was 0.79 degrees C between 1860 and 2019.

The temperature change from 1860 to 2019, as reported by HadCRUT4, shows an increase of approximately 0.79°C (1.4°F). That is less than one degree over 158 years. HadCRUT4 is the operator of the world’s observation data and is managed by the University of East Anglia in Australia.

C. The Temperature Anomaly was Overstated by 8.6%

HadCURT4 doubled the Northern Hemisphere (NH) land temperature over the Southern Hemisphere (SH) land temperature, because there is twice as much land in the NH. However, they failed to double the SH ocean temperature over the NH ocean by the size difference in the oceans. This resulted in a slight skewing of the temperature anomaly by 8.6%. The average global anomaly since 1860 should have been 0.73 °C.

D. There are Biases

There is a potential bias associated with the selection of the starting period or zero line. An arbitrary date can dramatically affect the results. As an example, the temperature measurement from 1860 to 2019 indicates an increase of approximately 0.79°C [HadCRUT4]. Tokyo Climate Center reported it as 0.67°C. But they used a different starting date or zero line. Based on historical records, the starting date should have been 11,000 years ago, which was when the current calm period started. There are other potential biases.

E. What are the Normal Temperature Fluctuations

Temperature anomaly fluctuations are normal and expected. Sea bed and ice core records show that normal fluctuations in the temperature anomalies vary by at least ± 2° C. This does not mean that higher or lower temperatures did not occur. They did. It is also true that these higher or lower temperatures do not mean the Earth will experience devastation. There have been many temperature fluctuations exceeding 10°C without significant consequences. This issue was discussed in Question 1, subpart B, and it is repeated in the supporting documentation in the link below.

F. Earth is Currently in an Ice Age

Many scientists, in the 1970’s were projecting an upcoming ice age.  But the Earth is currently in an ice age known as the Quaternary glaciation, which started 2.5 million years ago.  Ice ages are caused by long-term, orbital deviations known as the Milankovitch cycles. They are not caused by normal temperature fluctuations.  During an ice age there are several glacial advancing, retreating, and interglacial cycles.

G. Earth is Currently in a Long Term Cooling Period.

The figure to the left displays five million years of temperature change data. The temperature anomaly 5.4 million years ago was 4 degrees higher than it is today. The peak temperatures from 300,000, 400,000, and 100,000 years ago were also warmer than they are today. Overall, the figure indicates that the Earth is currently in a long-term cooling trend.

H. In 1970's Climate Scientists Projected a Cooling Trend

In 1972, a group of 42 top scientists wrote a letter to the president of the United States, reporting the start of a cooling trend.  In response, the US National Science Foundation began preparing potential actions to address the cooling trend.  These reports illustrate that short-term projections of global cooling or global warming are not credible predictors.  It takes at least a thousand years to establish a credible trend.


The reported world surface temperature change between 1860 and 2019 is 0.79 °C (1.4°F), but it contains an 8.6% error, on the high side. Today’s temperature anomaly is well within the normal fluctuations. And predictions based on periods of less than a thousand years are premature. The Earth is currently in a stable period.