Their complaint argues that plant operations emitted greenhouse gasses that contributed to global warming and rising sea levels that heightened hurricane damage.

The 5th U.S. Circuit, in Comer v. Murphy Oil--citing a recent U.S. Supreme Court decision accepting the plausibility of a link between emissions and hurricane severity--held that the plaintiffs had standing and should be allowed to proceed to establish that their injuries are "fairly traceable" to defendants' activities.

The 5th Circuit's ruling agreed with the reasoning in a ruling last month in Connecticut v. AEP by the 2nd U.S. Circuit Court of Appeals in New York, which allowed an action to go ahead that was brought by a coalition of state attorneys that declares carbon emissions by various power companies to be a public nuisance and seeks to have them capped and then reduce such emissions.

At the same time, in a ruling that is expected to be appealed, a U.S. District Court judge in San Francisco tossed out a case filed against oil and power companies by the Inupiat Eskimo fishing village of Kivalina, which argued the companies were causing global warming by raising sea levels that would put their town underwater.

Global warming actions in the Kivalina case, according to Mr. Nevius, have resulted in litigation over the scope of an insurer's duty to defend against such suits.

According to the attorney, on July 9, 2008, Steadfast Insurance Company filed a complaint in state court in Virginia seeking a declaration of no coverage for one of the underlying Kivalina defendants.

Steadfast, a subsidiary of Zurich Financial Services, alleged that it had no duty to defend its policyholder for three reasons: 1) lack of an "occurrence"; 2) a Loss In Progress Endorsement; and 3) application of a pollution exclusion.

Nevius said defending lawsuits such as the Kivalina case can be expensive, and while the underlying Kivalina case has now been dismissed, legal costs will continue to mount through the appeals process.

While many companies may think of "nuisance" suits alleging harm from their greenhouse gas emissions as unlikely to survive, Mr. Nevius said, he notoed that two have crossed important early hurdles on appeal in the last two months, adding that the cost of defending such suits can dwarf the costs of any potential judgment.

An insurance company's duty to defend, he explained, is broader than its duty to indemnify, and companies facing such suits should move quickly to secure coverage for defense costs, or prepare for more high-stakes coverage battles such as the Steadfast case.

If Steadfast prevails, in Nevius' view, insurance companies will be that much less likely to defend initially, and rather may simply deny defense coverage at the outset of any greenhouse gas-related suit seeking damages.

He observed that filing in Virginia may be a smart tactic by the insurance industry, because the Virginia Supreme Court has held that chlorine added to water by municipalities as a disinfectant falls within the purview of a pollution exclusion.

While the two federal appeals court rulings allowing greenhouse gas suits to go forward raise a warning flag to emitters, the lack of federal court unanimity also bolsters the case for insurance coverage for any related liability, according to Mr. Nevius, who is. an adjunct professor at Pace University School of Law, where he teaches a class on Climate and Insurance.

Given that the courts cannot agree on whether and how emissions of CO-2 and other greenhouse gasses give rise to actionable pollution, "it cannot be said with certainty that 'pollution exclusions' bar coverage. When uncertainty exists over coverage, the policyholder should receive the benefit of any doubt," he advised.

The attorney forecasted that continued uncertainty will be the rule as the gas-emission cases wind their way through the appeals process and the judiciary wrestles with who will bear the burdens of climate change.