There has been a lot of discussion about the difference between the satellite and station methods of measuring the global temperature and which is better. This is one of the more contentious aspects of the global warming debate. It gets people very agitated. There are serious problems and benefits with both methods, but my main method has been to compare their response to climate events. In that regard there is no question that the satellite method registers a greater response to events. This is shown in the following two posts.
I will not repeat any of the arguments from those articles here. Instead I will focus on the difference between the two methods and why I feel that the satellite method is more accurate and responsive at detecting changes in the global temperature.
The biggest difference to me is one of resolution. The station method uses thermometers that are located around the world and they measure the minimum and the maximum temperature each day. This is then averaged, adjusted and combined into the global average. Here is the list of stations used for the CRU temperature set. It contains the location of the 4,138 stations used to measure the global temperature.
Earth’s Surface Area = 510 million km2
CRU Stations = 4,138
Each station measures 123,265 km2
This leaves each station measuring an area of North Korea or the state of New Mexico depending on which one means more to you. While this is not a major problem by itself, these stations are not uniformly spread around the world.
In fact the real problem is that 46.7% of the worlds stations are located the region that covers only 4.8% of the worlds surface. North America is the region in the world that has enough stations that each station is covering less than 20,000 km2 per station. That means that outside of North America, the total station to area exceeds 230,000 km2. That is getting into the range of 1 station per area the size of the United Kingdom. It is even worse than that though. In many, many places there is not even a single station in a region that large.
Generally for the station method the Earth is broken into 5×5 grids of longitude and latitude. According to the MET office here is the spatial coverage of the Earth.
This does not tell the whole story either. This map shows ocean temperatures that have been interpolated from the HadSST2 data. This map shows the data that has not been interpolated for the ocean records.
There is also one final spatial problem with the station method. Here is the global breakdown of stations by continent.
That means there is exactly 1 single thermometer to cover an area the size of Spain. That is less than one thermometer to cover an area larger than the state of California. The warming in Antarctica is based on 60 years of records from only 23 stations on the entire continent. Antarctica is larger than the United States.
This is not a problem by itself. Such coverage can give an idea about the global temperature, but it will not be sensitive at detecting changes. An area the size of Spain can have entire storm systems that only cover a small percent of the area. It is not possible to accurately measure that much area with a single thermometer. This is the cause of the lower sensitivity that is statistically observed by using the station method.
The satellites have much greater precision. They have resolution at a scale of 4 km2. That is comparable to having a thermometer every 2km in every direction. This coverage is from 85N to 85S. Or an area that covers 99.6% of the Earth’s surface. That is the UAH coverage at least. The RSS is less as they cover from 80N to 70S. The resolution of both data sets is identical.
This allows the satellite method have the equivalent of 127,033,686 thermometers uniformly spread across over 99% of the Earth’s surface. Instead of big blocks to cover the Earth, they provide a fine picture of the Earth’s temperature. Here is the daily example of the Earth’s temperature.
Even the shapes of the current storm systems show up clearly in the satellite data. Such resolution is absolutely impossible by using the station method. This is why the satellite method is so sensitive at detecting changes in the Earth’s temperature.
What they measure is different. Instead of measuring the temperature at a single point a few feet off the Earth’s surface, the satellite method obtains the temperature of the bottom few kilometers of the Earth’s atmosphere. So not only does it measure with much finer resolution, it measures the temperature of a column of air.
The result is an anomaly map that is a much better representation of the atmosphere’s temperature. Here is the latest anomaly map as provided by the RSS.
The net difference is that the satellite method has the equivalent of 30,700 thermometers to each station method thermometer. When it comes to detecting changes in the Earth’s temperature, this is a truly significant difference. One that is easily detectable when comparing the response of each method to climate events like ENSO and volcanic eruptions.
Many, many problems can be found in any method of measuring the Earth’s temperature. Long articles have been written on extensive problems for both methods. I am sure that people will try to refer to those articles in the comments section. In the end, the satellites show a greater ability to detect changes in the Earth’s temperature. To me, those results matter.
If a group of scientists were to know nothing about the why that a measurement was made, but only knew the difference in resolution and saw the data that showed greater sensitivity, there is no question which method would be chosen. The only real problem that people have with the satellite method today is that it does not show as much warming in the past 30 years as they want it to. It doesn’t match up with their expectations, so they disregard it and use a litany of reasons to justify their dislike.
I will bet that if the satellite method showed twice as much warming as the station method with all other things being equal, the warmists would mock anyone who was skeptical of the satellite method. Since that is not the case, it will continue to be derided until the Earth is well into the next glacial period.