Using Paleo Evidence To Predict The Future

Understanding Earth's past climate behavior provides priceless insight into what it may do in the future. Long winters and glacial advances are recorded in proxy data from glaciers, sea ice, and soil samples. Deep-sea sediment cores show that icebergs traveled as far south as the waters off the coast of Portugal.

Scientists at NOAA use paleoclimatic data to identify abrupt climate changes. These intervals have occurred as global events and as local events; some severe, others less severe. NOAA experts have studied events that occurred hundreds to tens of thousands of years ago. During the Holocene (the past 11,000 years), several climate changes have been centered on drought events; many of these well-documented events coincided with the fall of great civilizations.

One thing scientists at NOAA have concluded is that from the existing proxy data uncovered so far, the climate has changed in the past much more rapidly and intensely than anything humans have seen during their existence on Earth. Many of the most abrupt climate changes have involved major changes in the ocean-atmospheric-ice-land systems.

Scientists test their theories against existing data, partly through the creation of models. Thus far, they have determined that Earth's climate system has two different stable modes, which it switches rapidly between. Over the last few hundred thousand years, the paleo record shows warm interglacial stages, which can last for 10,000 years or more, interspersed with glacial stages. Each of the glacial cycles on Earth is similar in terms of temperature and duration. Scientists would like a better understanding, however, of which mechanisms trigger the abrupt changes.

One thing they have a good understanding of is rapid ice-sheet melting in the transition from cold glacial periods to warm interglacial periods. This is supported by observation. Experts at NOAA are currently working on computer models and improving the algorithms to simulate climate change. Scientists there are also debating other causes of abrupt change. One issue that is highly debated concerns the atmospheric carbon dioxide levels that accompany the glacial-interglacial cycles. These are still not well understood and are viewed as an important piece of knowledge to have in order to restrict abrupt changes before they hap pen in the future and in order to plan for and protect society from the resulting negative impacts.

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