A leading climatologist is warning that nearly all of the computer simulations at the heart of the predictions of catastrophic, man-made global warming cannot be trusted with respect to a key measure.

At a meeting in the Palace of Westminster in London, Professor John Christy of the University of Alabama in Huntsville told MPs and peers the climate models are way off in their predictions of rapid warming at high altitudes in the tropics.

"They all have rapid warming above 30,000 feet in the tropics – it's effectively a diagnostic signal of greenhouse warming," he said. "But in reality it's just not happening. It's warming up there, but at only about one third of the rate predicted by the models."

Christy's remarks were highlighted by the Global Warming Policy Foundation, a non-partisan think tank in London. The group says that while it is "open-minded on the contested science of global warming," it is "deeply concerned about the costs and other implications of many of the policies currently being advocated."

Read a paper presenting Christy's key findings

Christy said a similar discrepancy between empirical measurements and computer predictions has been confirmed at the global level.

"The global warming trend for the last 40 years, starting in 1979 when satellite measurements began, is +0.13C per decade or about half of what climate models predicted," he said.

But Christy says climatologists aren't paying attention to the real-world data.

"An early look at some of the latest generation of climate models reveals they are predicting even faster warming. This is simply not credible," he said.

Many other scientists have pointed to failed predictions based on the models, noting a "pause" for the past two decades in the rise of average global temperatures.

Scientists who promote the theory of anthropogenic climate change contend a rise in the level of carbon dioxide in the atmosphere due to human activity is causing catastrophic warming.

But a new scientific study found that the current CO2 levels of 410 parts per million were last seen on Earth 3 million years ago. Researchers at the Potsdam Institute for Climate Impact Research concluded that temperatures were up to 7 degrees Fahrenheit warmer globally and sea levels were 65 feet higher.

Meanwhile, the millennial generation in America apparently is taking the climate models to heart. Two-thirds have nothing saved for retirement, and there are indications that the predictions of doom by politicians and many climatologists are to blame.