Jan. 22 (Bloomberg) -- Lawyers are becoming some of the best-paid environmentalists.

Twenty of the 100 highest-grossing U.S. law firms have started practices advising companies on climate change, according to a Bloomberg survey of the firms' Web sites. The attorneys help clients finance clean-energy projects and lobby Congress, typically billing $500 to $700 an hour.

Firms including Akin Gump Strauss Hauer & Feld, Heller Ehrman and Sheppard Mullin Richter & Hampton joined the global warming cause as real-estate and structured-finance attorneys lost jobs to the worst U.S. housing slump in 27 years. The move into climate-change law is gaining traction as Congress considers a mandatory carbon market to curb greenhouse gas emissions.

``Since the elections last November, climate change has had a higher profile as a political issue,'' said Paul Gutermann, co- leader of Washington-based Akin Gump's group, which comprises 50 of the firm's 1,023 attorneys.

Gutermann's team is helping clients including PG&E Corp. push U.S. lawmakers to establish a market that uses so-called carbon credits to penalize heavy polluters financially. Senators John Warner and Joseph Lieberman introduced a bill inspired by Europe's carbon market, and attorneys predict some legislation will pass after President George W. Bush, who opposes mandatory caps on emissions, leaves office in a year.

Global warming, driven by heat-trapping gases, is causing Arctic ice to melt and sea levels to rise, a United Nations panel of scientists said last year.

International Action

International reaction has sparked interest in reducing carbon dioxide emissions, making energy use more efficient and adding to non-polluting power sources.

Baker & McKenzie, a Chicago-based firm with 3,335 lawyers, was a pioneer, creating a climate-change group a decade ago. It became profitable after two years, said Richard Saines, who heads the U.S. part of the practice.

The 60-lawyer team brought in estimated revenue of $15 million to $20 million in 2007, Saines said. The firm's total revenue in 2006 was $1.52 billion, according to the trade magazine American Lawyer.

``We saw this as one of the key international-law issues that would affect U.S.-based multinationals,'' Saines said. ``And that is now the case.''

Saines and others wouldn't disclose how much they bill.

Hourly rates for climate-change partners at the biggest law firms in the largest U.S. cities are typically $500 to $700, said Chuck Wehland, an environmental partner at Washington-based Jones Day, which started a practice in 2001.

Lawyers' Fees

In the Midwest and Pacific Northwest, attorneys more often charge $300 to $500, said Rick Glick, president of the American College of Environmental Lawyers. The range is in line with fees for attorneys in other practice areas, said Edward Zaelke, a partner in the 28-person renewable-energy practice at New York- based Chadbourne & Parke.

PG&E paid Akin Gump $400,000 for lobbying Congress in the first half of 2007, according to a federal disclosure statement. Not all the activity was climate-related and the team did more than lobby, Gutermann said. He declined to elaborate.

Companies in all U.S. sectors are turning to lawyers to help them build systems to monitor, report and verify carbon credits, lawyers say.

The world carbon-trading market tripled to about $30 billion between 2005 and 2006, according to the World Bank. Such a market in the U.S. may reach as much as $300 billion by 2020, Peter Orszag, director of the Congressional Budget Office, said in U.S. House testimony last year.

European Model

The model proposed by Warner, a Virginia Republican, and Lieberman, an independent from Connecticut, is similar to the European Union's emissions program. Heavy polluters must buy credits to comply, while cleaner companies can profit by selling them.

``The idea is you let the people who are doing the polluting find the most efficient way to reduce pollution,'' said Robert Zwirb, a derivatives lawyer at New York-based Cadwalader Wickersham & Taft. ``If one utility can do it more cheaply than another, they engage in a trade. It's similar to swaps, only instead of dealing with interest rates, you're dealing with greenhouse gases.''

Akin Gump started its group two months ago with lawyers from existing practices expert on the environment, energy litigation, investments, project finance and public policy. San Francisco- based Heller Ehrman created its multidisciplinary team a year ago. Sheppard Mullin started a 50-member practice in May.

Growing Market

Building on existing clients, Los Angeles-based Sheppard Mullin has produced a ``substantial influx of work'' on land use, compliance and energy projects, said Randolph Visser, who heads a climate group comprised of 50 of the firm's 517 lawyers.

Customers include transportation companies in the Port of Los Angeles and FirmGreen Energy Inc., a closely held Newport Beach, California, developer of clean technology that the law firm is helping to negotiate a $25 million investment by Morgan Stanley.

``These are evolving marketplaces that require scrutiny by law firms to make sure we are in compliance and to take advantage of marketing opportunities,'' said FirmGreen Chief Executive Officer Steven Wilburn. ``If you just look at the hourly rate, it seems hard to justify. But if you look at the overall business plan, it's a cost you have to plan for.'' Wilburn would not disclose how much FirmGreen pays attorneys.

Climate-change attorneys also advise private-equity firms and hedge funds on clean-energy projects.

Energy Investments

Worldwide investments in sustainable energy sources such as wind, solar and water power rose 43 percent to $70.9 billion in 2006, according to a UN report.

In the U.S., more than $4 billion was invested in wind projects alone, according to Chadbourne's Zaelke, who specializes in financing and developing wind farms.

One of Zaelke's clients, John Deere Renewables, has invested more than $500 million since 2005 in community wind farms in seven states. The company, part of the financial services arm of Des Moines, Iowa-based Deere & Co., gets advice on supply agreements, project development and tax structures, said David Drescher, general manager of John Deere Wind Energy.

``They've been to a lot of wind farms,'' Drescher said.