— A decade after a vast power outage shut down the Northeast, the electricity grid remains "highly vulnerable" to blackouts because of extreme weather events fueled by climate change, a report issued Monday by the White House and the Energy Department concluded.

The Aug. 14, 2003, blackout occurred when an alarm failed in an Ohio utility control room, leading to a cascade of blackouts that affected 50 million people from Michigan to Massachusetts. But more recent power outages also have been caused by severe weather, such as storms in the East and wildfires in the West.

Between 2003 and 2012, about 679 blackouts occurred due to weather events, each affecting at least 50,000 customers. Over the same time period, weather-related outages cost the economy between $18 billion and $33 billion annually, depending on the number and severity of events.

"The aging nature of the grid — much of which was constructed over a period of more than one hundred years — has made Americans more susceptible to outages caused by severe weather," the report found.

The analysis of the power grid was conducted in response to a plan that President Barack Obama laid out in late June to combat climate change and better prepare for it. Already, weather shaped by human activity has hit the United States more rapidly than had been predicted, threatening infrastructure, water supplies, crops and shorelines, according to the draft Third National Climate Assessment, a federal report last issued in 2009.

Last year, superstorm Sandy knocked out power for 8.5 million customers. Strong winds from hurricanes and tornadoes are the main cause of the kind of infrastructure damage that leads to blackouts, the report said.

In Maryland, weather events including Hurricane Irene in 2011 and the June 29, 2012, derecho have prompted calls for hardening of the electricity grid. Both storms caused more than 750,000 Baltimore Gas and Electric Co. customers to lose power for an average of nearly two days, with many outages stretching up to a week.

"As these severe weather events are likely to occur more regularly in the future, it is essential that efforts to strengthen BGE's system against this potential threat accelerate and expand," the company said Monday in a statement.

Power plants, especially those that burn coal, contribute to climate change through emissions of heat-trapping carbon dioxide. Obama directed the Environmental Protection Agency to develop rules to curtail carbon dioxide released by new and existing power plants, with the next round of proposals due in September.

But while the new report on the power grid spotlights the system's vulnerabilities and offers suggestions for improvement, it also underscores how little the administration can do to boost electricity reliability.

Most utilities are publicly traded corporations and their activities are generally regulated by the states. The Obama administration allocated $4.5 billion for investments in energy efficiency and reliability systems, called "smart grid" technology, as part of its 2009 stimulus plan. But on a conference call to discuss the report, senior administration officials could not name other ways to drive improvement of the electricity network at a time when threats from climate change are mounting.

Asked about Monday's report, a Maryland Public Service Commission spokeswoman referred to an order regulators made in February calling on state utilities to improve reliability. The commission required utilities to submit plans to prevent or limit future weather-related outages and blackouts, and also signaled it may penalize them for "sub-standard performance" in restoring outages.

A plan BGE submitted in May called for expanding initiatives to make upgrades in areas most frequently hit with outages, more aggressively trim tree branches, and bury some power lines.

Upon full completion of the initiative, BGE said in its statement, the company expects to see improvement in electric reliability of about 10 percent. The company said it was also making other improvements beyond that initiative.

The national power grid report recommended replacing wooden utility poles with ones made of concrete, steel and other stronger material. Burying power lines is an oft-discussed option, but the report noted it is extremely costly and, in coastal areas, underground wires are vulnerable to flooding from storm surges.

The report also recommended greater use of distributed generation, or small-scale power sources, such as from renewable energy, that could be installed in communities or near critical facilities, such as hospitals, thereby avoiding outrages caused by downed power lines or flooded transmission substations.

Electric utilities have invested $478 billion in infrastructure improvements since 2007 and are expected to spend more than $90 billion annually on capital expenditures through 2015, said Richard McMahon, vice president of energy supply and finance at the Edison Electric Institute, a Washington trade group.

The American Society of Civil Engineers estimated that $673 billion in investments would be needed by 2020 to upgrade the grid to meet future demand. But the costs of such improvements are recouped through rate increases, often unpopular moves that need to be ratified by state regulators.

Baltimore Sun reporter Scott Dance contributed to this article.