David Roberts is staff writer at Grist.org. In "Climate Change is Simple" he describes the causes and effects of climate change in blunt, plain terms.

Clouds affect the energy Earth receives, keeps and emits back to space -- it's all a matter of balance. Dr. Bruce Wielicki is senior scientist for Earth science at NASA's Langley Research Center. His research has focused on clouds and their role in Earth's radiative energy balance for more than 25 years. He served as principal investigator on NASA's CERES science team and as co-investigator on the CALIPSO missions. NASA is now gearing up for a mission to compile the most accurate climate data ever. Dr. Wielicki is Mission Scientist for CLARREO which will provide accurate, credible and tested climate records that lay the groundwork for decisions on policies that address the effects of climate change on society.

As the 2013 president of the American Meteorological Society, Shepherd is a leading international expert in weather, climate and atmospheric sciences, and recently briefed the U.S. Senate on climate and extreme weather. A professor in the Department of Geography at the University of Georgia, Shepherd is director of the University's Atmospheric Sciences Program. Shepherd spent 12 years as a research meteorologist in the Earth-Sun Division at NASA-Goddard Space Flight Center. Shepherd was recently named the UGA Athletic Association Professor in Geography and 2004 was honored at the White House by President Bush with a PECASE award as one of the top young scientists and engineers in the country.

Oceanographer for the U.S. Navy, RADM David Titley discusses the hot topic of climate change, and its impending ramifications on national security. Listen as he details some of the top facts and figures you should know about climate change and your future, explained in terms that even the most unfamiliar with science would be able to understand.

Top climate scientist James Hansen tells the story of his involvement in the science of and debate over global climate change. In doing so he outlines the overwhelming evidence that change is happening and why that makes him deeply worried about the future.

Michael Mann is a professor in the College of Earth and Mineral Sciences, a climatologist, and the director of the Earth System Science Center at Penn State University. Michael is best known for his extensive background and research in the field of paleoclimatology. This work led to Michael's graph of temperature trends over the last thousand years, popularly coined as the "hockey stick graph" because of its resemblance to the sporting equipment.

One of the world's top climate diplomats, John Ashton is now an independent commentator and adviser on the politics of climate change. From 2006-12 he served as Special Representative for Climate Change to three successive UK Foreign Secretaries, spanning the current Coalition and the previous Labour Government. He was a cofounder and, from 2004-6, the first Chief Executive of the think tank E3G. From 1978-2002, after a brief period as a research astronomer, he was a career diplomat, with a particular focus on China. He is a visiting professor at the London University School of Oriental and African Studies, and a Distinguished Policy Fellow at the Grantham Institute for Climate Change at Imperial College.

David Bromwich on Global warming - fact or fiction?