The Wonderful Issues of Climate Change - Post #2 - Measuring Global Warming

Original Date: January 10, 2024; Updated: January 14, 2024 and February 25, 2024

Author: Tim Platnich

In the Post on Climate and Weather, I focussed on the definition of 'climate' relative to 'weather. In this post, I will talk about the 'change' part of climate change.

Some decades ago, the term widely used was 'global warming'. Over the years, this term was largely replaced by 'climate change'. Notwithstanding the change in terminology, the problem remains the same: global warming. It is warming that is said to drive climate change.

When we talk about 'change' or 'warming' we are speaking relatively. Change means the present, relative to another point in the past. Similarly, warming suggests an increase in temperature today relative to another point in the past.

Typically, global warming talks about an increase in the “earth’s average or mean surface temperature”. Temperature is defined as the measure of the average kinetic energy of the particles in a given volume of substance or mixture at a point in time. Temperature is measured, scientifically, in Kelvins, or more commonly in degrees Celsius. Unfortunately, in the US the Fahrenheit scale is still in use (largely outside of the scientific community). One sees in many publications the use of degrees F.

Obviously, the earth does not have one temperature at any given time. Temperatures vary all over the earth at different times and in the different media of land, water and atmosphere. Temperatures can differ hour by hour and kilometer by kilometer. They can vary by latitude and longitude. They can vary by depth below the surface of land and of water. They can vary by altitude above the surface of land or water.

Because there is no one temperature of the earth, averaging of temperatures is required. This is a statistical exercise of some complexity. An average is one of an infinite arrays of values that may be used to represent a given collection of numbers. In very basic terms, the ‘mean’ or ‘average’ is the value arrived at by adding together a given set of numbers then dividing that sum by the amount of numbers in the set. “[T]he earth’s average temperature” is not a physical measurement but rather is a calculated statistic [“Taken by Storm”, Essex and McKitrick, Revised Edition 2007].

The values being averaged are the collection of temperatures gathered, from time to time, around the world either directly through recording (and extrapolation) or indirectly through proxies related to temperature.

Surface temperature measurements, via thermometers, go back about 150 years. Thermometers were not uniformly located over the years. Many parts of the world had no thermometers. Other parts of the world were over-represented. This lack of uniformity requires adjustments in global surface temperature calculations using models. Some of these adjustments are controversial.

There are land surface measurements, ocean surface measurements and atmosphere measurements. Land surface measurements have traditionally been made at weather stations located at or near airports and population centers. Consequently, urban areas may be over-represented in land surface measurements. This is known as the urban island effect.

Ocean surface measurements historically were made by passing ships which didn’t go everywhere. More recently they are made using buoys located at a number of fixed points in the ocean. Buoy measurements have vastly improved temperature recordings over the last two decades.

Measurements of atmospheric temperatures have been made by weather balloons and more recently by satellite. Satellite measurements have only been taken over the last 50 years or so.

Differences in measurement techniques and technologies must be considered when comparing the past to the present. For example, temperature sensors rather than thermostats are now being used in various places.

For global temperatures prior to 1850, proxies must be used in place of thermometer measurements. Proxies involve the measurement of temperature-sensitive properties of material preserved from the past. ["Unsettled", by Steven Koonin]. Examples of proxies include: tree rings; water in deep bore holes; cores drilled into ice sheets; cores drilled into ocean sediment and speleothems (stalagmites and stalactites). Proxy measurements are not as accurate as direct thermometer measurements because other confounding variables may be involved. For example, tree growth is also sensitive to precipitation, not just temperature. Proxy measurements, particularly those going back 2000 years, have been controversial.

Global warming is a relative concept. Global warming is determined by comparing the statistical global average temperature at a previous point in time with the statistically calculated global average temperature at a subsequent point in time. Typically, global warming is determined by comparing the last 30 years of global mean surface temperatures with the temperatures from a 30 year period before 1900. Thirty year time frames are common as this length of time coincides with the notion of climate as opposed to weather. Shorter periods may be used, but comparing one year to another is not considered a comparison of climates.

Generally, global warming is measured back to about 1850. There are various reasons for this. One reason is that direct measurements of temperature prior to that date were scarce. Another reason is 1850 roughly represents the start of the industrial revolution. The start of the industrial revolution is when humans began to emit substantial CO2 into the atmosphere. As we shall see in subsequent posts, it is largely the emissions of CO2 into the atmosphere that is said to be causing global warming, directly or indirectly.

The starting point for measuring average surface temperatures is important. If the starting point is 1910, the earth has warmed about 1.3 degrees C. ["Unsettled"]. If the starting point is the average from 1951 to 1980, the warming would be .9 degrees C.["Unsettled]. If the starting point is 1000 AD, warming to date would be about .4 degrees C.["Unsettled"]. Some studies suggest that temperatures during the Medieval Warming Period [generally considered to be between about 950 and 1250 AD] were higher than temperatures today (or at least up until the last decade). [“The Hockey Stick Illusion” by A.W. Monford].

According to IPCC AR6, the average global surface temperature between 2001 and 2020 was between .84 and 1.1 degrees C higher than in the period 1850 to 1900. This implies a temperature increase of about .99 degrees C since 1850 - a .99 degrees C increase in 170 years, or 17 decades. This equates to about .06 degrees C per decade on a linear basis. Note the precision of the temperatures! Certainly, thermometers in 1850 did not measure temperature to 1 hundredth of a degree. Remember, average global surface temperatures are a statistic, not a measurement.

Climate is more than just temperatures. Hence, climate change measures other aspects of climate that has changed such as precipitation, droughts, wind, and so on. In this respect, comparisons must be made to the past. Unlike measuring average temperature, it is non-sensical to try and average precipitation, droughts, etc. These aspects of climate are necessarily regional. So the question must be: has the climate of western North America changed? Is there more or less precipitation? Are there more or less wind events? Is there more or less flooding? These questions must be asked concerning dozens if not hundreds of different regions.