Tropical Climate Change

The tropics receive the lion’s share of incoming solar radiation and are the primary heat reservoir for the Earth's climate; heat export from the tropics via the ocean and atmosphere is a fundamental component of global climate dynamics. The warm tropics also fuel the global hydrologic cycle. The changes that occur in the modern tropics on interannual times scales have a tremendous impact on global climate, i.e., ENSO and a significant body of research suggests that global teleconnections would be strong on all time scales.  Hence, a better understanding of the character and the causes of tropical climate variability as well as their possible global teleconnections are key issues for global climate research.  Our group studies changes in tropical climate that have occurred in the past and seek to understand what they mean for modern observed changes as well as anticipated changes in the future.

In our research, we ask such questions as:

• Is there evidence for tropical temperatures as warm as today during times in the recent past, such as the “Medieval warm period”, the Holocene “climatic optimum”, and warm interglacials (Marine Isotope Stages 5 and 11)?
• How cold were the tropics during key time intervals such as the Little Ice Age, the Younger Dryas, and the Last Glacial Maximum?
• How did tropical temperatures and the hydrologic cycle change in the past, from tectonic to glacial-interglacial to abrupt time scales, and what are the linkages to extra-tropical climate?
• What was the response of the Asian monsoons, the Intertropical Convergence Zone, and other aspects of the tropical hydrological cycle to changing insolation?
• Have there been large changes in the amplitude and frequency of tropical interannual variability (e.g. ENSO) on decadal, millennial and orbital times scales?
• How will the coupled ocean-atmosphere system in the tropics respond to future natural and anthropogenic forcings?

To address these and related questions, we use a variety of proxies preserved in archives as diverse as sediment cores, speleothems, and corals, as well as global circulation model output for sensitivity studies and data-model comparison.

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