Further scientific evidence that global warming starting to run out of steam over two decades ago has been presented by an international group of leading scientists. In a major re-evaluation of data from meteorology balloons rising through the troposphere, the scientists confirmed that temperatures have mostly paused since around 1998. The discovery can only add to pressure to re-open the so-called ‘settled science’ debate around global warming and the central part it plays in the 30-year rush towards Net Zero.
Readings throughout the troposphere, Earth’s lower atmosphere that extends in parts up to 15 km altitude, have been available for many years. The researchers were able to use measuring metadata to improve the consistency of records obtained from almost 700 global locations, recording twice a day since 1978, at 16 pressure levels. The slowdown since 1998 observed in the balloon data is confirmed by accurate satellite data, which also shows a current pause of about 91 months. An earlier pause from 1998 to 2012 has been largely wiped from all the major surface temperature datasets.
The two graphs show the results from the study for the northern hemisphere and the tropics at a height of about 11 km. Most of the warming over the last 40 years occurred up to the late 1990s. The tropics have warmed less than the north, and in fact at 11 km it is difficult to discern any significant warming in the tropics at all.
The temperature variations recorded in the lower troposphere are generally reflected at higher altitudes, notes Emeritus Professor Ole Humlum in his recent “State of the Climate” report. At higher altitudes, near the tropopause, the temperature patterns seen lower down can still be recognised, “but for the duration of the record (since 1979) there has been no clear trend towards higher or lower temperatures”, said Humlum.
There is little scientific dispute that warming and cooling in the troposphere reflects that found at the surface. Most atmospheric gas is contained in this area, including the so-called greenhouse gases such as water vapour, carbon dioxide and methane. Just before COP26 last year, the World Economic Forum published scientific research that claimed around 80% of the increase in the temperature of the troposphere since 2000 was due to warming caused by humans. This was said to show that the effects of fossil fuels and human activity “are infiltrating all our surroundings, even those high above our heads”.