Last week, three spills of potentially carcinogenic hazardous chemicals at a natural gas drilling site in Pennsylvania prompted the state’s environmental protection agency to suspend Cabot Oil & Gas's operations in the county.

The spills were just a small part of a larger phenomenon — accidents at natural gas drilling sites that have imperiled the drinking water of nearby communities in states from Pennsylvania to Wyoming and that have no governmental oversight.

 They call it the “Halliburton Loophole” — an exemption for oil and gas companies to inject hazardous materials directly into or near underground drinking water supplies in a process called hydraulic fracturing.

At the United Nations this week, representatives of 85 governments, including 14 heads of state, assembled in a room to discuss how to change a world in which forests are worth more dead than alive.

Deforestation accounts for 20% of global greenhouse gas emissions — more than Europe emits, and more than all the world’s cars, trucks, boats and planes emit. Because trees absorb carbon, deforestation causes a large amount of the greenhouse gas to be released to the atmosphere and also prevents trees from continuing to absorb it.

A leading solution that the world leaders were discussing is REDD, Reducing Emissions from Deforestation and Forest Degradation, a UN program that would give people in developing countries a financial incentive to preserve their forests and, in the process, immediately begin reducing the world’s carbon emissions.

While environmental advocates still have serious concerns about high carbon emitters abusing the system and simply buying forest credits to avoid making their own emissions cuts, the idea behind REDD is popular and could be adopted in December at the international climate change talks in Copenhagen. However, many in the room noted that while plenty of countries verbally expressed support in expanding REDD beyond the pilot stages, few had made the true commitment of devoting funding.

Nuclear power has long been controversial for its radioactive waste, history of dangerous meltdowns and potential to help spread nuclear weapons. With those arguments against it, and with a spotty record of construction and management in the 1970s and 1980s, the United States hasn’t welcomed a new nuclear power plant since 1996 – and that one had been in the works since 1973.

Now, however, fears about climate change, along with changes in the industry and in regulatory practices, are changing the nuclear energy calculus.

“Nuclear right now is at a crossroads. There are a lot of possibilities that nuclear can make a good contribution to solving the greenhouse problem, but those possibilities are just ifs,” says John Parsons, executive director of the Center for Energy and Environmental Policy Research at MIT and an author of a widely cited report, The Future of Nuclear Power.

Nuclear power will almost certainly be part of climate legislation discussed in the U.S. Senate. Environment and Public Works Committee Chairwoman Barbara Boxer (D-Calif.), who is writing the Senate's version of the climate bill, was clear about that last week, saying, “There will be a nuclear title in the bill.”

But a new study tallying the cost of nuclear power suggests that nuclear's many uncertainties could push it out of the realm of being cost-competitive.

As Congress debates climate legislation, critics are pounding their fists about costs, arguing that the United States can't afford to take action during a recession and calling the House-passed American Clean Energy and Security Act (ACES) the biggest tax in U.S. history.

Government analyses from the Environmental Protection Agency and Congressional Budget Office have already concluded that the wild claims about costs are exaggerated, with ACES’s price over a decade likely to be around $24 billion.

What is eye-popping instead, experts say, are the cost of doing nothing to forestall climate change.

“Every time economists look at this, it becomes clear that the costs of doing nothing are quite high, and that is something that is missing in the domestic debate,” says Brenda Ekwurzel, climate scientist with the Union of Concerned Scientists.

“Most people are thinking only about the cost of mitigating climate change without knowing anything about the costs of doing nothing about climate change.”

The Economics of Climate Adaptation Working Group, which was created by the Global Environment Facility and includes reinsurer Swiss Re and consulting firm McKinsey & Company, released a report on Monday showing that failing to take action to stop climate change could cost vulnerable nations, such as flood-prone Guyana, up to 19% of their gross domestic product by 2030. Island nations and coastal communities like the low-lying Maldives, already threatened by rising seas, are weighing an even more expensive mass relocation of their people.

Such losses will grow worldwide without swift international action, the World Bank says in its World Development Report 2010, released today. The report finds that flooding, droughts and other climate change disasters will cost African and South Asian countries up to 5 percent of their GDP if temperatures rise more than 2 degrees Celsius from pre-industrial levels.

"Climate change is costly, whatever the policy chosen," the World Bank says, but it warns that "spending less on mitigation will mean spending more on adaptation and accepting greater damages: The cost of action must be compared with the cost of inaction."

In 1609, the English maritime explorer Henry Hudson arrived in New York Harbor on an expedition for the Dutch.

Four hundred years later, as New York City faces the ramifications of climate change, it is learning from the Dutch how to manage rising sea levels, which could rise as much as 55 inches by 2100.

On September 9th and 10th, a conference in New York City will examine the challenges coastal cities face in the 21st century. Held by the Henry Hudson 400 Foundation, the H209 Forum will bring together leaders from both the U.S. and the Netherlands, a country that has long battled flooding, with more than a quarter of its lands lying below sea level.

“It’s a good chance to look into the Dutch water case – how do they do it? Obviously, the Netherlands has had a long history of struggling and living with the water,” says Gert Tetteroo, the executive director of the Henry Hudson 400.

Although New York City sits above sea level, it has important infrastructure, including its subway system and traffic tunnels, below sea level. Also, parts of downtown are only 1.5 meters, or 59 inches above sea level. As sea levels rise, the city will become more susceptible to dangerous storm surges and the flooding they would bring.

As college students return to school, they will be discovering subtle changes designed to reduce their climate footprints, from new low-energy lighting and renewable power sources to the removal of cafeteria trays to cut back on wash time.

In recent years, universities across the United States have taken it upon themselves to reduce their environmental impact. Their students, fully aware that climate change will be one of the greatest challenges of their generation, and outside sources such as the College Sustainability Report Card and Princeton Review are carefully scrutinizing and encouraging their efforts.

So far, 650 schools – home to about a third of all college students nationwide – have signed the American College and University Presidents’ Climate Commitment to become carbon neutral and produce zero net emissions, coming close to creating the nation's "first sector-wide commitment to climate neutrality,” says Toni Nelson, program director for ACUPCC. And many prominent schools that have not signed, including most of the Ivy League and Stanford University, already have strong sustainability programs in place.

“One of the driving forces behind the commitment is that if you can graduate climate-literate graduates in every area – people who are going to become leaders in business, government, non-profit organizations and legal systems, etc. – if you can get a shift happening in their education and climate-literacy, then you shift the whole culture around climate,” Nelson said.

Due to popular demand, Congress just extended the cash for clunkers program with an additional $2 billion allocation, allowing consumers to continue trading in older cars with low fuel-efficiency for newer, slightly more fuel-efficient ones.

The program will stimulate the automotive industry as inventories clear and production increases for at least another month or two before the program runs out of funding again, but its environmental impact will be negligible. Even with the extension, the cash for clunkers program will have the effect of stopping the entire country's emissions for less than three hours per year.

A new Senate bill introduced last week, however, could have a longer-term environmental impact and improve the fuel-efficiency of all cars, not just clunkers.

Senator Jeff Bingaman (D-N.M.), along with Senators Olympia Snowe (Rep.-Me.), John Kerry (D-Mass.), and Richard Lugar (Rep.-Ind.), introduced the Efficient Vehicle Leadership Act, which proposes a “feebate” system, based in part on recommendations provided by the Rocky Mountain Institute.

Feebate programs, already adopted in France and Finland and being considered in California, will reward purchasers of more fuel-efficient cars with rebates while levying fees on those who buy less fuel-efficient cars.

On Tuesday, a non-partisan government agency released an analysis of the climate change bill being considered by Congress, examining what impact the pending legislation would have on energy markets and the economy.

The Energy Department’s Energy Information Administration (EIA) projected that the American Clean Energy and Security Act would, by 2020, result in an $134 a year increase in an average household’s energy bill. Immediately, both proponents and opponents of the bill began touting the estimate – which projected a modest increase in energy prices through the year 2030 – as bolstering their side’s argument.

ACES proponents said the increase, roughly 23 cents a day, was nominal, while opponents called it an energy tax.

But in the back and forth, an important point was obscured: the report showed wide-ranging uncertainty over how effective the bill will be in meeting one of its primary goals -- reducing the emission of greenhouse gases from capped sources of pollution in the United States.

That's because a safety valve built into the bill – carbon offsets – makes it possible for polluters to pay someone else to reduce emissions instead.

ACES proposes to cut emissions of the greenhouse gases responsible for global warming several ways, including a cap-and-trade program, an improvement in technologies like carbon capture and storage and nuclear energy, and the buying and selling of carbon offsets.

If ACES passes, the amount of carbon dioxide companies can emit will be capped. If they emit more than that limit, they can meet the target by paying for a reduction of greenhouse gases elsewhere, thus offsetting their excess emissions.

But the rules are so complicated that the outcome is actually a big guessing game, even for the EIA.

While economists bemoan the rising U.S. unemployment rate, nearing 10 percent, there's a part of the country that has long struggled with unemployment many times higher – the Navajo Nation.

The unemployment rate across the sprawling region is 44 percent right now. But on Tuesday, its leaders approved groundbreaking legislation that they hope will bring change for their people.

The Navajo Nation became the first Native American tribe to pass green jobs legislation intended to grow thousands of jobs in ways that follow the Navajo traditions of respecting the Earth. The Navajo Nation Council voted to establish a Navajo Green Economy Commission that will draw on federal, state and foundation funding to pay for green initiatives ranging from farmers’ markets to small-scale energy projects.

“This is huge,” says Wahleah Johns, Field Organizer for Black Mesa Water Coalition, part of the Navajo Green Economy Coalition, which lobbied for the legislation.

“One of the largest indigenous nations in the U.S. is paving a pathway for green jobs development in Indian country. It could be a model for most Indian nations throughout the world.”

Over the past week, federal regulators have begun to tighten environmental rules for mining operations. They’re taking steps in the right direction, environmental advocates say, but only baby steps – much more is needed.

One of the moves by regulators would strengthen the permitting process for mountaintop mining in Appalachia, but still allow the practice to continue. Another would require certain mining companies to have sufficient finances for cleaning up their sites, a rule intended to keep fly-by-night operations from dumping that burden on taxpayers.