Using Analogue Past Climate to Understand Future Evolution of Current Climate
Climate changes in the early Pliocene period (~3-5 million years ago) are often considered the closest analog to today’s global warming. It is believed that the external factors controlling the Pliocene climate system–the intensity of sunlight incident on Earth’s surface, global geography, and the atmospheric concentration of CO2 (350-400 ppm)–were similar to present-day conditions. A recent study led by DOE-funded researcher Professor Alexey Fedorov of Yale University creates a reconstructed latitudinal distribution of sea surface temperatures for the Pliocene. This reconstruction shows that the difference in temperatures between the equator and subtropics was greatly reduced during this period, leading to a permanent El Niño-like state with global impacts on climate. In contrast, El Niño-like states only occur intermittently today during the warm phase of a quasi-periodic climate oscillation that impacts weather and climate patterns worldwide every 4-5 years. The authors concluded that models simulating the early Pliocene climate may need to incorporate additional mechanisms for increased ocean heat uptake when simulating the early Pliocene climate to account for the permanent El Niño-like state during that period. These findings are relevant to current discussions about global warming due to the enormous impacts of changes in Earth’s warm pool, such as dramatic shifts in global precipitation patterns and cloud cover, and tentative evidence that the tropical belt has again been expanding poleward over the past few decades as it did during the Pliocene.
Brierley, C.M. A.V. Fedorov, Z. Liu, T.D. Herbert, K.T. Lawrence and J.P. LaRiviere Greatly Expanded Tropical Warm Pool and Weakened Hadley Circulation in the Early Pliocene. Science (2009). Science Express, DOI: 10.1126/science.1167625.