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Global Climate Models

Global Climate Models


Thank goodness for tech heroes who design, build and operate very powerful computers. Computer models are mathematical statements of hypothesized relationships between causes and results that the model addresses; a “computer simulation” involves running the model and seeing what comes out. The determinants of “climate,” which on Earth consists of many regional climates, is extraordinarily complex. It is very difficult to estimate with confidence the total effects of changes in any climate variable, even with many data points and the fastest computers, but the tech guys try.

Complexity produces uncertainty and surprises, sometimes unpleasant ones. The journal “Science” has published a study, funded by NASA, hypothesizing that global warming will accelerate destruction of the ozone layer in earth’s stratosphere. Ozone ten miles and more above the Earth’s surface protects us from the sun’s cancer-causing ultraviolet rays, but it is vulnerable. Scientists in the 1970s linked chlorofluorocarbons (CFCs) used as refrigerants with observed thinning of the ozone layer, and with human cancer. The world responded with the Montreal Protocol phasing out CFC production in the 1980s, but it will take decades for CFCs to be fully cleansed from the stratosphere.

CFCs do their ozone-layer killing when the CFC molecules fall apart and release chlorine. The chemically-active free chlorine then destroys ozone in complex chemical reactions. Until recently, we only worried about the sun’s ultraviolet rays breaking up the CFCs, but the Science study says that global warming adds a new threat. More intense storms have begun to push warm, moist air 12 miles up, where the storm’s heat and water vapor may cause CFCs to decay into more free, ozone-eating chlorine.

Climate scientists do not yet understand why storms get into the stratosphere or how often that will happen, but they are concerned. Mario J. Molina won a Nobel Prize for 1970s research linking CFCs and ozone depletion. He states that the study adds “one more worry to the changes that society’s making to the chemical composition of the atmosphere” – that more powerful storms could cause significant ozone depletion at latitudes where billions of people live.

This blog talks about “climate change” and related concepts frequently, and abbreviated IPCC definitions of some of those terms, as contained in SREX, may be helpful:

Adaptation: In human systems, the process of adjustment to actual or expected climate and its effects, in order to moderate harm or exploit beneficial opportunities.

Climate Change: A change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.

Climate Extreme (extreme weather or climate event): The occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable. For simplicity, both extreme weather events and extreme climate events are referred to collectively as ‘climate extremes.’

Disaster: Severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery.

Disaster Risk Management: Processes for designing, implementing, and evaluating strategies, policies, and measures to improve the understanding of disaster risk, foster disaster risk reduction and transfer, and promote continuous improvement in disaster preparedness, response, and recovery practices, with the explicit purpose of increasing human security, well-being, quality of life, resilience, and sustainable development.

Image by Jimbo Wales, Fredrik [GFDL ( or CC-BY-SA-3.0 (], via Wikimedia Commons


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