Frances Beinecke, 02/21/13

President, Natural Resources Defense Council

Climate change is already threatening our communities with extreme weather and costly damages. Fortunately President Obama has the power to stop a major source of global warming pollution from spreading: tar sands oil.

Richard Schiffman, 02/21/13

Journalist

Climatologists tell us that the climate change train has long since left the station, but perhaps it is not yet too late to prevent it from accelerating beyond our capacity to cope.

Joe Keefe, 02/21/13

President and CEO, Pax World Funds

We need to deploy a host of strategies to address the developing catastrophe of climate change, and we must do so with a sense of urgency and resolve. As investors, there are essentially three approaches we can take to investing in fossil fuels.

Neil Wagner, 02/21/13

Creator, 'What on Earth?' Comic Strip

Whether you are convinced our weather is undoubtedly affected by anthropogenic climate change, or feel that conclusion is a bit too emphatic, would you say rolling the dice with our climate is a good gamble? After all, you should never bet that which you can't afford to lose.

Hans Zimmer, 02/21/13

Composer

Artists, can touch millions of people with a song, book or movie, and can play a key role in moving the global economy toward a greener future. The time to act is now. We need sustainable, low-carbon economies that create more and better jobs.

Kyle Rabin, 02/21/13

Program Director, GRACE Communications Foundation

Recent extreme weather events, oil spills and increasing food prices tell us that we can no longer view our food, water and energy systems in isolation. This means gaining a better understanding of how these three systems connect and then taking carefully considered actions to ensure food, water and energy security and sustainability for the future.

Brian Czech, 02/20/13

President, Center for the Advancement of the Steady State Economy

In the real world, economic growth means more economic activity, more population × consumption, more GDP. It means more greenhouse gas emissions, less biodiversity, and a growing ecological footprint.

Bill Chameides, 02/20/13

Dean, Duke University's Nicholas School of the Environment

The bottom line is recycling is good, but it's not going to get us even close to the goal of zero landfill waste. A consumer economy centered around compostable products is a lot sounder and could even be tasty.

Dean Kuipers and David Levine, 02/20/13

If your Manhattan bedroom is under 6 feet of water (and can be again), or millions of cows can't find one green blade of grass because of drought, or all the polar bears die because we lose the Arctic sea ice, do we really care if the solution creates jobs?

Mike Sweeney, 02/20/13

Executive Director, The Nature Conservancy of California

There's an incredible diversity of nature in California, and we now have more national parks than any other state to prove it. There is really no better place to experience all the central coast has to offer than at Pinnacles National Park.

Anjali Sareen, 02/20/13

News Editor, The Huffington Post

It's worth noting that many people would shudder at the idea of squirting bodily fluid from an animal directly into their mouths, but those same people drink milk freely and happily because it's packaged to look pretty and marketed to us as a health food.

Seth Baum, 02/20/13

Executive Director, Global Catastrophic Risk Institute

It could be difficult for human civilization to survive a global catastrophe like rapid climate change, nuclear war, or a pandemic disease outbreak. But imagine if two catastrophes strike at the same time.

Peter H. Gleick, 02/20/13

President, Pacific Institute

It turns out there are real jobs to be had in the water sector if we make the investments that are needed in water supply, deliver, treatment, and smart management. Millions of jobs.

Bill Radvak, 02/20/13

President and CEO, American Vanadium Corp

As always, it is a buyer-beware world, where extensive scrutiny must be made regarding the management, values and actions of a company before making an investment. For those who make wise selections for their alternative energy portfolio, great riches may be had.

The University of Central Florida Forum, 02/20/13

Opinion series by faculty, staff and students of UCF

Oysters also filter water -- a lot of water. Scientists estimate that each oyster filters 50 gallons of water each day. That equates to about a bathtub's worth of water filtered by each oyster each day!

John Fullerton, 02/20/13

Founder and President, Capital Institute

My daughter and I joined an estimated 50,000 demonstrators in Washington D.C. marching against the XL Pipeline that would connect the Canadian Tar Sands to American refineries. After a half century on this planet, I took to the streets. Here's why.

Dr. James Hansen, 02/19/13

Climatologist

The climate science is crystal clear. We cannot go down the path of the dirty fuels without guaranteeing that the climate system passes tipping points, leaving our children and grandchildren a situation out of their control, a situation of our making.