National Science Foundation
To What Degree What Science Is Telling Us About Climate Change Leading climate change experts discuss one of the most complex scientific puzzles ever to confront humankind.
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How Do We Know?
Introduction: Why study climate change?
What are some of the climate change projections made by the
      Intergovernmental Panel on Climate Change?

How do we know the earth is warming?
How much has the earth warmed recently?
Why is it important to reconstruct the long history of the earth's climate,
      and how can we do that?

If the earth has warmed before, why be concerned now?
What is unusual about the earth's warming during the past century or so?
What does carbon dioxide have to do with global warming?
What is the source of the increased greenhouse gases in the atmosphere?
How do we know the rising carbon dioxide is not part of a natural cycle?
How do we know the warming is caused by rising levels of carbon dioxide?
How much warming do we face, and what are the uncertainties involved?
How are climate models being improved?
Would reducing greenhouse gas emissions avoid the impacts of
      climate change immediately?

How close are we to having all the answers?
Intergovernmental Panel on Climate Change
What is the IPCC and what's it like to participate in that process?
What steps are involved in creating an IPCC assessment?
Why does it take years to put together one IPCC Assessment Report?
Who approves the IPCC documents that are provided to policymakers?
What makes IPCC assessments different from other scientific assessments?
Once the scientists review all the literature, how do they debate individual scientific issues?
What are the chances the IPCC is over- or underestimating the impacts of climate change?
How is the IPCC assessing climate change, even as the science behind it evolves?
How has the scientific consensus evolved from the first IPCC report in 1990 to the most recent?
Why hasn't the IPCC suggested public policies based on its findings?
The Carbon Cycle
Much of the carbon we are burning is not staying in the atmosphere. What's happening?
Where does the carbon in the atmosphere come from?
How does carbon get into the oceans, and how much is in there?
Is the oceans' ability to absorb carbon decreasing?
How will increased amounts of carbon affect plants and animals?
Plants need nitrogen. Can they get enough to meet the increased levels of carbon dioxide?
What will increased carbon do to life in the oceans?
Are there surprises in the carbon cycle that could lessen climate warming or make it much worse?
Is there a carbon tipping point after which climate change consequences will become dire?
Water Cycle
How will climate change affect the water cycle?
How will climate change affect drought in the western United States?
How will climate change affect water supplies in the western United States?
What is land use change and how does that affect the water cycle?
If climate change impacts the water cycle, how might it affect natural land cover?
Does the ocean reveal anything about the impact of climate change on the global water cycle?
How do changes in ocean salinity affect the ocean?
Earth's Heat Balance
How does the sun's energy get into the climate system?
How does heat get distributed around the world?
How are scientists monitoring carbon dioxide around the globe?
What about indirect effects of greenhouse gasses? Do they increase warming or reduce it?
What role do clouds play in warming or cooling the earth?
What are aerosols and will they warm or cool the planet?
Can aerosols be used to slow the warming of the planet?
Climate Modeling
What is a computer climate model?
How do you begin to model the climate?
How do scientists know if computer models are simulating climate change correctly?
How can the findings of paleoclimatologists help validate climate models?
Are there some predictions that climate modelers are more certain of than others?
What are some of the limitations of current climate models?
Scientists need computers to create climate models. Is the technology keeping up with their needs?
Can hurricanes be accurately modeled in a computer?
What Americans Believe About Climate Change
How do people decide whether or not they believe climate change is real?
How has media coverage of climate change affected Americans' views on the issue?
Do scientists confuse the public about whether they agree on climate change?
Where does the public rank climate change compared to other problems facing the world?
Is it true that people only care about climate change if it affects them personally?
Does concern about climate change vary by age group?
What's driving many Americans to reduce their carbon footprint?
How do Americans feel about the various possible solutions to the climate change problem?
Do Americans favor governmental action to address climate change?
Does the public want government to require industry to take climate change-related actions?
How important is social science to understanding the future of climate change?
History of Climate Change Research
How has climate change research evolved over time?
When did people first believe it might be possible for them to influence climate?
When was it first determined that greenhouse gas emissions were causing warming?
What was the original link between the military and climate science?
When were increasing levels of atmospheric CO2 first documented?
What was the origin of climate modeling?
How did climate change become a major area of study?
There had been a belief that the Earth was cooling, not warming. What changed?
When did we learn that climate change involves more than just the warming of the planet?
How has NSF supported climate change research?
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