How Ominous is the Premonition of Future Global Warming?

TL;DR

This paper critically assesses the future climate predictions of general circulation models (GCMs) using a Bayesian model selection approach, finding that current models may overstate the severity of future global warming.

Contribution

It introduces a Bayesian multiple testing framework for evaluating GCM predictions, applying Gaussian process emulation to assess the validity of future warming scenarios.

Findings

Selected GCM models do not convincingly support current warming patterns.

Results challenge the alarming future global warming predictions.

Forecasts do not indicate drastic future temperature increases.

Abstract

Global warming, the phenomenon of increasing global average temperature in the recent decades, is receiving wide attention due to its very significant adverse effects on climate. Whether global warming will continue even in the future, is a question that is most important to investigate. In this regard, the so-called general circulation models (GCMs) have attempted to project the future climate, and nearly all of them exhibit alarming rates of global temperature rise in the future. Although global warming in the current time frame is undeniable, it is important to assess the validity of the future predictions of the GCMs. In this article, we attempt such a study using our recently-developed Bayesian multiple testing paradigm for model selection in inverse regression problems. The model we assume for the global temperature time series is based on Gaussian process emulation of the black box scenario, realistically treating the dynamic evolution of the time series as unknown. We apply our ideas to datasets available from the Intergovernmental Panel on Climate Change (IPCC) website. The best GCM models selected by our method under different assumptions on future climate change scenarios do not convincingly support the present global warming pattern when only the future predictions are considered known. Using our Gaussian process idea, we also forecast the future temperature time series given the current one. Interestingly, our results do not support drastic future global warming predicted by almost all the GCM models.