Measuring the temperature of a human is easy. The temperature of a pet is similarly uncomplicated, if a bit rude. The temperature of a planet on the other hand, is far more challenging. The temperature is not the same everywhere, so a thermometer can not do it. Weather stations ashore near population centers are relatively common, but even outlying areas and the vast oceans need to be represented.
In addition to this geographic spread, researchers must address the reality that various issues, such as equipment changes, must be in place to ensure that the data is consistent over a century or more.
A handful of teams worldwide manages surface temperature data sets separately, including NASA, NOAA, the UK Met Office, and the Japan Meteorological Agency. The differences between their results are so small that only climate scientists could find them remarkable. They all show pretty much the same global warming over time. But that has not stopped conspiratorial critics from claiming that temperature measurements are somehow manipulated to create the appearance of warming where none exists. (These critics never explain how this cabal led by scientists to shrinking glaciers, the rising sea and migratory species.)
Fortunately, there are many ways to examine the accuracy of records of surface temperature. One of these possibilities is to compare them to the satellite measurements of the last decades. But that too is harder than it sounds. The satellite data sets most commonly used and current longest actually measure higher temperatures in the atmosphere (which is not exactly like the surface behavior), the satellites have to consider their own technical problems, and the data covers a number of different satellite That's not always easy to synchronize with each other.
A new study uses a newer option: the Aqua Satellite, launched in 2002 by NASA. Among the instruments of this satellite is the measurement of infrared radiation the surface of the earth. This differs from the instruments of these other satellites, which measure the microwave radiation emitted by gases in the atmosphere. With around 1
A team led by Joel Susskind of NASA compared Aqua satellite data with multiple surface temperature data sets. The results confirm (again) that surface data provide an excellent estimate of global change, as opposed to conspiracy theories. However, as the satellite also measures areas where surface measurements are sparse, it indicates what surface data is missing.
Starting with the global average, there is a solid match between the satellite and surface datasets at all timescales. The period 2003-2017 is short enough to anticipate small differences in the warming trend of each dataset, but they are quite close. The satellite data show the biggest warming trend at 0.24 ± 0.12 ° C per decade. The four surface records compared over the same period were between 0.17 and 0.22 ° C per decade.
The major differences are in areas such as the Antarctic, Arctic, and Central Africa, where surface measurements have to be extrapolated in relatively few places. In accordance with previous research, surface temperature data underestimate the satellite's warming trend in the Arctic. At the same time, parts of the Southern Ocean around the Antarctic cooled slightly more than was recorded by the surface data.
The results should not be too surprising if you had previously assumed that scientists could figure out how to work with thermometers. But because these scientists need to sweat the details, this type of research is a valuable counter-stroke, showing that things work just fine – but also where edge enhancements can be made.
Environmental Research Letters, 2019. DOI: 10.1088 / 1748-9326 / aafd4e (About DOIs).