Climate shapes our lives and structures our world. Climate determines how we live, when and where food can be grown, and where the different ecosystems that support life on the planet thrive. As a result, any change in climate will affect each and every one of us. Many scientists are concerned that global warming, from an increase in carbon dioxide and other gases in the atmosphere, may change Earth's climate considerably within the next century. The urgent need for knowledge about the pace, causes, and consequences of climate change is underscored by the fact that more than half of the overall research effort and resources at Scripps Institution of Oceanography is currently tied to studies of Earth's climate. Data from powerful global observation systems and from intriguing detective work on the history of Earth's climate have greatly advanced our understanding of climate change over the past few years.
Studying Our ClimateThere is no longer much uncertainty over whether our planet is warming. Most scientists agree that the average temperature of Earth's surface has increased about 1° F over the last century. Based on climbing carbon dioxide levels, climate models predict warming of another 3°F in the next 50-100 years.The upward temperature trend has been accelerating since the 1970s, with many of the warmest years occurring within the past decade and a half. Many scientists are concerned that global warming, from an increase in carbon dioxide and other gases in the atmosphere, may change Earth's climate considerably within the next century.
How do scientists know what Earth's climate was like 1,000 years ago? The thermometer wasn't invented until 1592, and temperatures have only been accurately measured in enough locations to be useful for global climate studies since about 1880. Natural time capsules hold the answer.
Time CapsulesTrees, corals, polar ice caps, and seafloor sediments faithfully record environmental conditions in their layered structure. With some scientific ingenuity, these layers can be read like chapters of a history book on Earth's climate.
Trees and corals exhibit annual growth rings that reflect climatic conditions over their lifetimes, which can span hundreds of years. The most valuable climate records come from very old, slow-growing trees and corals that inhabit pristine areas. Protecting these living climate archives and their habitats from human impacts thus preserves information about Earth's history not recorded anywhere else.
Glaciers high on mountaintops are tens of thousands of years old in some places, and polar ice sheets have accumulated over hundreds of thousands of years. Bubbles of ancient air, as well as volcanic ash, pollen grains, and other airborne clues to climate, are trapped in the layers of ice.
On the ocean floor, layers of mud have accumulated over millions of years, preserving the remains of tiny plants and animals that fall to the bottom. These microfossils provide clues to climatic conditions at the time the organisms lived.
Scientists use these natural climate records to extend our instrument records of temperature and rainfall back in time. Viewing current climate change in this larger context is helping us understand the ways in which human activities are affecting Earth s climate system.
Greenhouse GasesMany scientists believe Earth's climbing temperature is mainly due to the buildup of greenhouse gases in the atmosphere. Carbon dioxide (CO2) is generated when carbon-based fuels such as coal, petroleum, and natural gas are burned in electrical generation plants and vehicles. Devegetation of land surfaces also contributes to CO2 buildup. In the 200 years since the Industrial Revolution began, the amount of CO2 in Earth's atmosphere has increased by about 30%. Methane, generated by agriculture and the breakdown of human waste, has increased by 150%.
With the help of natural climate records, the effects of human actions can be put into a much larger perspective. According to ancient air bubbles trapped in polar ice caps, CO2 is more abundant today than it has been in the last 160,000 years.
Gases like carbon dioxide and methane in earth's atmosphere act just like the glass of a greenhouse to trap heat. Without an immediate change in personal and business activities, doubling of this gas is a virtual certainty in the coming decades. According to computer models, this will likely drive world temperature up another 3 8 degrees Fahrenheit! Some of the consequences of this warming are predictable, but there will also be many unpredictable effects. Scientists are uncertain, for example, how global warming will alter regional weather patterns.
Feeling the EffectsMelting of the arctic ice cap has begun to separate polar bears from the seals they rely on for food. Glaciers atop mountains in Bolivia and Peru the sole source of drinking water for towns at the base of the mountains are expected to disappear in as little as 50 years as a result of global warming. Melting of the world s great ice sheets is contributing to a steady rise in sea level. Farmers on low-lying Pacific islands are already reporting that seawater is seeping into their fields, making them too salty to grow staple food crops. On the other side of the globe, the Florida Keys are drowning. Temperature-sensitive coral reefs around the world are also being devastated by increasing ocean temperatures.
Take stock of your own energy use
For more information visit Birch Aquarium's award winning Climate Change exhibit Feeling the Heat.
For further reading, these books and others are available in the Aquarium Bookshop:For children
Brian Cosgrove, Weather, Eyewitness Books, 1991.
Fiona Watt and Francis Wilson, Weather and Climate, Usborne Publishing Ltd., 1992.
-- Debbie Zmarzly, Ph.D., Science Specialist, November 1998.