Discussions of our proximity to a "global tipping point" on climate have now become commonplace. Today the carbon dioxide concentration in the atmosphere is about 385 parts per million -- more than 100 parts per million higher than before the Industrial Revolution. Just when and where the climate will begin to change in large, unpredictable ways remains a threat that all our environmental models say is coming, even if they cannot be forecast with any real accuracy. James Hansen, the tremendously well-respected climate scientist and director of the NASA Goddard institute for Space Studies, has often been quoted on this topic. "We don't understand how fast ice sheets can respond," Hansen said in a podcast interview with Earth & Sky. "But what we're learning

At a recent Capitol Hill hearing I was surprised to learn that it was far from common knowledge just how competitive wind power has become. As a result, a bit of a data and price update memo may be of use, even to those who follow the industry. In addition, I will summarize the data on a few of the least cost wind farms in the nation.

Wind energy in the United States has continued to grow, and represented 19 percent of the new nameplate capacity added to the electrical grid in 2006 . With a total cumulative U.S. capacity of 11,575 MW (1 percent of total U.S. nameplate capacity) at the end of 2006, wind energy is now often directly cost competitive with fossil-fuel generation, and at times is a least-cost supply option.

Representative Wind Project and Wind Power

The risks of climate change and, of course, high oil prices have unleashed a wave of interest and commitment to changing our energy economy that, perhaps, could safeguard the planet. City, state, federal and international proposals and legislation are today all in play -- and in flux -- to lay out targets for greenhouse gas reductions.

Some of the most notable are the 25 percent reduction in GHG emissions by 2025 and the 80 percent reduction by 2050 that California has adopted, the 70 percent or more reductions proposed in the United Kingdom, New Zealand, and the Japanese proposals, and the 100 percent fossil-fuel-free plans of Sweden, and a number of progressive cities intent on making climate-wise statements.

How these diverse and ambitious plans pan out is anybody's

Over the next five decades progress to meaningfully address the risk of significant climate change will require an estimated 80 percent, or more, reduction in the global emissions of greenhouse gases. From the baseline in 2007 of over seven billion tons of greenhouse gas emissions, three-quarters of which comes from fossil fuel combustion (with the remainder largely from land conversion and forest burning), the reductions required are from a global emissions portfolio that is currently increasing.

As the largest current emitter, at roughly 25 percent of the global total -- but more importantly as the nation with the largest energy resource and research base to affect change -- the United States and its inaction on climate protection for the last several years is poised to play a

Energy and climate are now all over the news these days. Remarkable agreements between many an erstwhile nemesis -- Democrat and Republican, environmentalist and venture capitalist, public official and industry leader, evangelist and reductionist/rationalist/scientist/atheist -- show that they are now, roughly, on the same wavelength.

In fact, the convergence is so strong that there is an evolving common international language around the need to investigate not just the science of global warming, but the specific local impacts of change -- from flooding to Great Britain, to hurricanes in the United States, to changes in ocean chemistry and coral growth. Global warming has, for many become a common language of carbon management. There is a recognized need to explore the

Solar photovolaics (PV) have undergone a remarkable evolution, really a transformation, since the beginning of the industry in the 1960s. Initially solar was so expensive -- well over $100 per kilowatt hour -- that only super-high value or remote applications, such as satellite and spacecraft missions, could be justified.

Following the OPEC embargoes of the 1970s, a wave of investment took place in the industry that, while brief, helped to bring a number of largely silicon-based technologies to niche markets. Since then scientific and materials engineering progress in the solar field has been steady, with an evolution away from silicon as the only material, to a truly exciting and promising range of plastic, thin film, nano-based, and organic cells.

While the potential

In the 1970s the big thing in vehicles, fuels and the environment was "get the lead out," an effort to remove lead from gasoline. After initial uncertainty and some opposition, the transition to unleaded fuels proved both remarkably easy and effective. I.Q. levels in children in urban America rose in direct response to the reduction in ambient lead levels.

Those really were the good old days in transportation. In addition to the lead phase-out a well-planned and sustained effort to raise average vehicle efficiency standards (the CAFE, or Corporate Average Fuel Economy) increased vehicle mileage standards by a quarter.

Sadly, that effort was not sustained, and vehicle efficiency levels have not changed significantly for over 25 years. These changes illustrate

In order to survive and thrive in the face of climate change, we need to establish and then put into practice -- as quickly as possible -- markets that utilize the value of carbon. The development of human civilization has followed a series of scientific and technological innovations -- starting with harnessing fire and domesticating plants and animals, the evolution of increasingly convenient energy sources, powerful personal communications and computing devices -- that have made our relatively quick progress possible. Looming advances include distributed energy systems, nanotechnology, and the pervasive use of genetic technologies for plants, and potentially for humans as well. But as a physicist who is focused on energy science, technology and policy related to climate change and