[00:09] Climate change isn't new. Earth's climate began evolving with the birth of the primitive atmosphere more than 4-billion years ago.

[00:18] Most variations in the Earth's climate system occur on timescales longer than a human lifetime; hundreds to thousands of years.

[00:26] Some changes, however, happen within decades and can greatly affect our lives.

[00:31] The extreme drought of the 1930's is a poignant example of how climatic variations can profoundly impact not just landscapes, but the people who make their livings in them.

[00:42] We now understand that human land use practices were partly responsible for the devastation during the Dust Bowl years.

[00:49] To what extent to we as humans affect our natural environment? From water supply management and agricultural practices to urban sprawl and the burning of fossil fuels, most scientists agree that human activities today are impacting virtually all aspects of the environment including climate.

[01:08] Understanding what part of climate change is due to humans and what part is due to natural variations is critical. By unraveling human induced from natural affects, we can decide which of our actions need to be modified.

[01:22] An experiment is underway with uncertain consequences. How will the Earth respond to the changes humans add to those nature has been producing for eons?