There are lots of reasons. Many of them can be found at my page on the subject — in the text, the list of related readings, and the list of related posts. Here’s the main one: Surface temperature data — the basis for the theory of anthropogenic global warming — simply do not support the theory.
As Dr. Tim Ball points out:
A fascinating 2006 paper by Essex, McKitrick, and Andresen asked, “Does a Global Temperature Exist.” Their introduction sets the scene,
It arises from projecting a sampling of the fluctuating temperature field of the Earth onto a single number (e.g. , ) at discrete monthly or annual intervals. Proponents claim that this statistic represents a measurement of the annual global temperature to an accuracy of ±0.05 ◦C (see ). Moreover, they presume that small changes in it, up or down, have direct and unequivocal physical meaning.
The word “sampling” is important because, statistically, a sample has to be representative of a population. There is no way that a sampling of the “fluctuating temperature field of the Earth,” is possible….
… The reality is we have fewer stations now than in 1960 as NASA GISS explain (Figure 1a, # of stations and 1b, Coverage)….
Not only that, but the accuracy is terrible. US stations are supposedly the best in the world but as Anthony Watt’s project showed, only 7.9% of them achieve better than a 1°C accuracy. Look at the quote above. It says the temperature statistic is accurate to ±0.05°C. In fact, for most of the 406 years when instrumental measures of temperature were available (1612), they were incapable of yielding measurements better than 0.5°C.
The coverage numbers (1b) are meaningless because there are only weather stations for about 15% of the Earth’s surface. There are virtually no stations for
- 70% of the world that is oceans,
- 20% of the land surface that are mountains,
- 20% of the land surface that is forest,
- 19% of the land surface that is desert and,
- 19% of the land surface that is grassland.
The result is we have inadequate measures in terms of the equipment and how it fits the historic record, combined with a wholly inadequate spatial sample. The inadequacies are acknowledged by the creation of the claim by NASA GISS and all promoters of anthropogenic global warming (AGW) that a station is representative of a 1200 km radius region.
I plotted an illustrative example on a map of North America (Figure 2).
Notice that the claim for the station in eastern North America includes the subarctic climate of southern James Bay and the subtropical climate of the Carolinas.
However, it doesn’t end there because this is only a meaningless temperature measured in a Stevenson Screen between 1.25 m and 2 m above the surface….
The Stevenson Screen data [are] inadequate for any meaningful analysis or as the basis of a mathematical computer model in this one sliver of the atmosphere, but there [are] even less [data] as you go down or up. The models create a surface grid that becomes cubes as you move up. The number of squares in the grid varies with the naïve belief that a smaller grid improves the models. It would if there [were] adequate data, but that doesn’t exist. The number of cubes is determined by the number of layers used. Again, theoretically, more layers would yield better results, but it doesn’t matter because there are virtually no spatial or temporal data….
So far, I have talked about the inadequacy of the temperature measurements in light of the two- and three-dimensional complexities of the atmosphere and oceans. However, one source identifies the most important variables for the models used as the basis for energy and environmental policies across the world.
“Sophisticated models, like Coupled General Circulation Models, combine many processes to portray the entire climate system. The most important components of these models are the atmosphere (including air temperature, moisture and precipitation levels, and storms); the oceans (measurements such as ocean temperature, salinity levels, and circulation patterns); terrestrial processes (including carbon absorption, forests, and storage of soil moisture); and the cryosphere (both sea ice and glaciers on land). A successful climate model must not only accurately represent all of these individual components, but also show how they interact with each other.”
The last line is critical and yet impossible. The temperature data [are] the best we have, and yet [they are] completely inadequate in every way. Pick any of the variables listed, and you find there [are] virtually no data. The answer to the question, “what are we really measuring,” is virtually nothing, and what we measure is not relevant to anything related to the dynamics of the atmosphere or oceans.
I am especially struck by Dr. Ball’s observation that the surface-temperature record applies to about 15 percent of Earth’s surface. Not only that, but as suggested by Dr. Ball’s figure 2, that 15 percent is poorly sampled.
Take the National Weather Service station for Austin, Texas, which is located 2.7 miles from my house. The station is on the grounds of Camp Mabry, a Texas National Guard base near the center of Austin, the fastest-growing large city in the U.S. The base — which is mostly bereft of vegetation — is adjacent to one of the major highways that runs through Austin. As I have shown elsewhere, the general rise in temperatures recorded at the weather station over the past several decades is fully explained by the urban-heat-island effect due to the rise in Austin’s population during those decades.
Further, there is a consistent difference in temperature and rainfall between my house and Camp Mabry. My house is located northwest of Camp Mabry, in a topographically different area. The topography is typical of the Texas Hill Country, which begins about a mile or east of my house and covers a broad swath of land stretching as far as 250 miles from Austin.
Getting down to cases. I observed that in the past summer, when daily highs recorded at Camp Mabry hit 100 degrees or more 52 times, the daily high at my house reached 100 or more only on the handful of days when it reached 106-110 at Camp Mabry. That’s consistent with another observation; namely, that the daily high at my house is generally 6 degrees lower than the daily high at Camp Mabry when it is above 90 degrees there.
As for rainfall, my house seems to be in a different ecosystem than Camp Mabry’s. Take September of this year: 8.0 inches of rain fell at Camp Mabry, as against 12.0 inches at my house. Thus far in October the total for Camp Mabry is
3.7 6.2 inches, as against 5.1 7.3 inches at my house. (Updated at 5:30 p.m. CT, 10/16/18.)
So the climate at Camp Mabry is not my climate. Nor is the climate at Camp Mabry typical of a vast area in and around Austin, despite the use of Camp Mabry’s climate to represent that area.