UCLA study yields more accurate data on thousands of years of climate change

UCLA Newsroom: Using a cutting-edge research technique, UCLA researchers have reconstructed the temperature history of a region that plays a major role in determining climate around the world.  The findings, published online Feb. 27 in the journal Nature Geoscience, will help inform scientists about the processes influencing global warming in the western tropical Pacific Ocean.

The study analyzes how much temperatures have increased in the region near Indonesia, and how ocean temperatures affect nearby tropical glaciers in Papua New Guinea and Borneo. Researchers also evaluated the accuracy of existing climate model predictions for that region. The findings illustrate that the region is very sensitive to climate change and that it has warmed considerably over the last 20,000 years, since the last ice age.

The team chose the specific area examined in the study because it is Earth's warmest open ocean region and a primary source of heat and water vapor to the atmosphere. As a result, temperature changes there can influence climate not just regionally, but globally.

"The tropical Pacific ocean-atmosphere system has been called a sleeping dragon because of how it can influence climate elsewhere," said lead author Aradhna Tripati, a UCLA assistant professor in the departments of Earth, planetary and
space sciences, and atmospheric and oceanic sciences.

...As part of the study, Tripati and her colleagues also investigated what sets the past and present height of glaciers in the tropics, and why they have been retreating. To accurately estimate the height of tropical glaciers and average temperatures at altitude in this region, they found that atmospheric mixing, through a process known as entrainment, needs to be factored in.

"We found that the large amount of ocean warming goes a long way to explaining why glaciers have retreated so much," said Tripati, a faculty member in the College of Letters and Science and a member of UCLA's Institute of the Environment and Sustainability. "Throughout the region, they have retreated by close to a kilometer since the last ice age, and are predicted to disappear in the next one to three decades. Previously understanding this large-scale glacial retreat has been a puzzle. Our results help resolve this problem."...

A NASA image of the Grasberg (Freeport) copper mine pit is in the foreground, and remnants of Indonesia's Puncak Jaya glaciers behind