Greenhouse gas emissions pose a serious threat to public health and welfare, according to an official finding issued recently by the Environmental Protection Agency.This may sound like old news, coming from the nation’s lead environmental agency, but the long-awaited “endangerment— finding marks a turning point in the U.S. response to climate change — the first step to regulating greenhouse gas emissions under the Clean Air Act. The EPA was required to make its finding in response to the landmark Supreme Court ruling Massachusetts vs. EPA, issued in April 2007.[IMGCAP(1)]We applaud the EPA’s decision; however, we also believe that addressing climate change requires broader legal authority to do the job right. There is no disputing that the Clean Air Act has served the country well in making major progress toward achieving its air quality goals: getting lead out of gasoline, reducing acid rain pollution and addressing urban smog.But climate change poses a unique challenge. Crafting an effective response will involve every sector of our economy, and the current Clean Air Act was never designed for this purpose. Any significant EPA action is certain to be met with a barrage of lawsuits that could delay progress, if not prevent it entirely. Rep. John Dingell (D-Mich.), the longtime chairman of the House Energy and Commerce Committee, predicted a “glorious mess— if the EPA moves forward without explicit guidance from Congress.Only Congress can change the collision course we’re on. We need Congress to take bold action by adopting a comprehensive climate change and energy policy that will strengthen our economy, create new job opportunities and leave a better environment for future generations of Americans. Congress needs to step in.We hold no illusions in terms of the challenges we face in addressing the threat of climate change. Moving from a high-carbon economy to a low-carbon economy will be a major undertaking. But the EPA’s endangerment finding makes it clear that the consequences of inaction will be staggering. According to the report, climate scientists are predicting rising sea levels, more intense storms, severe heat waves, increased flooding and an increase in the size and number of forest fires and insect outbreaks, among other effects from human-induced climate change.If we face this challenge head-on, we have the opportunity to reduce our dependence on foreign energy supplies and make the United States a global leader in clean energy technologies. As the economy returns to form, we need to have rules in place that will guide capital spending and allow companies to make the right business decisions. This process begins by placing a price on carbon emissions through a mandatory cap on carbon emissions that declines steadily over time.Climate change policy must also protect consumers by adopting aggressive energy-efficiency programs. This will reduce emissions and give us a powerful tool to help households and businesses manage their energy bills. States that have embraced aggressive energy-efficiency programs and standards have already proved that.We call upon Congress to put the appropriate framework in place to begin the transition to a 21st-century economy. As two of the nation’s leading energy companies, we stand ready to help transition our nation to a low-carbon economy.Ralph Izzo is president, chairman and CEO of Public Service Enterprise Group. Tom King is president of National Grid. PSEG and National Grid are both members of the Clean Energy Group.