BIG PICTURE:
In 2007 PhD climate scientist Richard Lindzen said the following about the 'hot spot' signature of the greenhouse warming effect:
"Roughly speaking, the (tropospheric) warming in the tropics is about two to three times larger than near the surface regardless of the sensitivity of the particular (climate) model.
This is, in fact, the signature (or fingerprint) of greenhouse warming.
Stated somewhat differently, if we observe warming in the tropical upper troposphere, then the greenhouse contribution to warming at the surface should be between less than half and one third the warming seen in the upper troposphere."
The hot spot is supposed to be an accumulation of hot air over the tropics.
It is supposed to be caused by higher levels of water vapor in the air, which is claimed to be a positive feedback (result) of higher levels of greenhouse gases, such as carbon dioxide, in the air.
But positive feedback is a stupid theory, never proven, and makes no sense -- positive feedback causes system instability, and would have resulted in runaway warming long before humans existed.
Our planet has had more CO2 in the air than today for most of its existence -- yet there has never been runaway warming -- if there had been, we would not be here today to discuss climate change!
If the tropical hot spot does not exist, then the hypothesis that global warming is caused by manmade emissions of carbon dioxide is falsified.
DETAILS:
The tropical hot spot is supposed to be one of three primary symptoms of global warming from greenhouse gasses.
The other two are significant warming, and ice melting, around the North and South poles.
But there is no melting of 98% of the ice around the South Pole.
There is melting of the tiny Antarctica Peninsula that extends way out into the ocean -- that peninsula is only 2% of Antarctica -- and it is being warmed by underseas volcano(s) and ocean current shifts, not greenhouse global warming.
The remaining 98% of Antarctica has no warming.
The EPA claimed enhanced warming in the tropical troposphere was a “fingerprint” of greenhouse gas global warming.
There is no tropical hot spot, nor has one ever been measured ... yet the alleged “tropical hotspot” was relied upon by the EPA to declare carbon dioxide a pollutant (actually a left-wing fantasy).
In fact, more CO2 in the air would be a blessing, not pollution.
CO2 is necessary for green plant life.
More CO2 in the air would accelerate green plant growth rates.
The optimum CO2 level for maximum growth of plants used for food is likely to be in the 1,000 to 2,000 ppm range -- 2.5x to 5.0x the current CO2 level of 400 parts per million concentration.
From a new report by economist James Wallace, climatologist John Christy and meteorologist Joseph D’Aleo:
The new Wallace, Christy, D'Aleo report is titled:
“On the Existence of a ‘Tropical Hot Spot’ Research Report and the Validity of EPA’s CO2 Endangerment Finding”.
Using statistical analysis, three independent scientists, James Wallace, John Christy, and Joseph D’Aleo tested the hypothesis that there is a warming trend over the tropics centered at about 10 kilometers, or 6 miles, or 33,000 feet up.
That "hot spot" was called a human fingerprint of warming at the November 1995 meeting of the of the UN Intergovernmental Panel on Climate Change (IPCC) scientific group in Madrid, by John Houghton and Benjamin Santer.
The "hot spot" was featured in AR-2 -- the 1996 assessment report of the IPCC.
The report rejects the hypothesis that any tropical hot spot exists, based on analyses of five different temperature data sets for the tropics, dating from 1959 to 2015.
"These analysis results would appear to leave very, very little doubt but that EPA’s claim of a Tropical Hot Spot, caused by rising atmospheric CO2 levels, simply does not exist in the real world.”