The Climate is Changing, but is it Changing as it was in the Past?

Are modern climate fluctuations merely naturally occurring events? Or are they the result of post-industrial products such as increased greenhouse gases?

Using a theorem and observational data from the Northern Hemisphere, Researchers from Oak Ridge National Laboratory (ORNL) and Penn State University have shown that fluctuations in climate are not possible from an unchanging statistical distribution for data taken during the industrial era.

This confirms what climatologists have been suggesting, that Earth’s climate statistics has been changing dramatically, in the post-industrial era. They recount their results in a paper titled Uncertainty in Climate Science: Not Cause for Inaction.

The researchers also address some people’s suggestion that it is not possible to have confidence in climate projections because there are too many uncertainties in current climate models.

Specifically, they used present and recorded-past observational data to produce statistical models of natural and anthropogenic carbon dioxide to complement a simple energy balance model to first track observational measurements of the global earth temperature, and then to make statistical forecasts into the future.

The outcomes, in the mean, are consistent with global climate models for the next 100 years because the nature and amplitude of the variability does not overwhelm the mean prediction. This suggests that if a complex model can capture the recorded observational variability, it should be able to have reasonable bounds of uncertainty in making relatively short predictions (approximately 100 years) of Earth’s climate. Moreover, the variability inherent in the anthropogenic carbon input is not capable of overwhelming the dramatic increasing shift of its mean, using reasonable bounds on uncertainty. This is not the case with the natural sources of variability.

This is work by ORNL’s Juan Restrepo, who is an American Physical Society fellow and Section Head of the Mathematics in Computation Section at ORNL, with an appointment in the mathematics department at the University of Tennessee-Knoxville. Michael Mann is director of the Earth System Science Center at Pennsylvania State University and a renowned climatologist.

The researchers will discuss their work at the APS March Meeting in Chicago. APS is the country’s foremost professional physics organization and boasts more than 50,000 members worldwide.

Provided by Oak Ridge National Laboratory.

Our Climate Has Changed. How Do We Learn to Live With Extreme Events?

Graph of temperature dataCREDIT: Juan M. Restrepo and Michael E. Mann

Temperature anomaly retrodiction and forecast (colored), as a function of the equivalent climate sensitivity (ECS) and the climate record up to the present (black). The retrodiction and the prediction curves are generated taking into account uncertainties due to CO2 emissions, volcanic activity, solar forcing. Stochastic variability due to temperature uncertainties has been included as well. The stochastic model for temperature fluctuations is informed by historical temperature variability data. From top to bottom, ECS = 4.5, 3, 2.5, 2, 1.5.