With the 2006 fire season hard upon us, wildfires already are racing through tens of thousands of acres of dry brush, destroying homes and other properties and triggering the declaration of a state of emergency in San Bernardino County. And now, there are new, very credible scientific reports that global warming is making the wildfire problem much worse.

It is too early to tell whether this fire season will equal the 2003 season, when more than 4,300 fires consumed nearly 660,000 acres in Southern California. But the evidence that wildfires have become more common and more destructive is undisputable.

Since 1986, wildfires in the western United States have struck with nearly four times the average frequency they did from 1970 to 1986. The total area burned during this period is more than 6.5 times the previous level. Last year's wildfire season was the worst on record, with more than 8.53 million acres burned nationwide.

In response to the increased threat to lives, properties and habitat from wildfires, I worked with a bipartisan coalition of senators to pass into law the Healthy Forests Restoration Act.

The focus of this legislation was forest management. For decades, brush-clearing ground fires had been suppressed, resulting in huge fuel loads of small trees and brush - perfect kindling for catastrophic fires.

The Healthy Forests Act established an expedited process for the Forest Service and the Department of Interior to work on brush-clearing projects that help minimize fire risk. Up to 20 million acres of lands near communities, municipal watersheds and other high-risk areas were included.

The bill increased funding for these projects, with at least 50 percent of the funds designated for fuels reduction near communities. Projects targeted the removal of small trees and brush, while protecting large fire-resilient old-growth trees.

A new study published online a week ago in the prestigious journal Science showed that warming temperatures played the biggest role in recent wildfire increases. In particular, researchers found that wildfire frequency was correlated with the timing of the spring snowmelt. In the West, spring and summer temperatures for 1987 to 2003 increased more than 1.5 degrees Fahrenheit over those for 1970 to 1986. These warmer temperatures created prime conditions for destructive fires - an earlier snowmelt, and a longer (78 days longer, according to the study) and drier fire season.

I am not surprised by this finding. Every day, we learn more about the detrimental effects that global warming is having on our planet. From coral reefs dying because of higher seawater temperatures to cannibalism in polar bears caused by reduced sea ice preventing them from hunting their usual prey to the extinction of the golden toad in Costa Rica because of the disappearance of the mist that protected them from a killer fungal disease, warming is causing major changes around the world.

Global warming is real, and it may make the wildfire problem worse in many ways. For example, destructive bark beetles are attracted to burned forest areas, but their spread is also facilitated by warmer temperatures. Some, like the mountain pine beetle, were controlled in the past by die-offs during cold spells.

But now, thanks to warmer winters, populations are exploding. In 2003, the mountain pine beetle killed 60 percent of the ponderosa pine trees across 474,000 acres of the San Bernardino and San Jacinto Mountains. Beetle-killed trees may become fuel for fires, which may attract more beetles to the area, in a vicious circle.

Some have claimed that the new Science study on warming and wildfires shows that the Healthy Forests Act is on the wrong track, because this policy focuses on forest management rather than on mitigating the effects of climate change. But the study itself makes a more nuanced point. In the Rockies, where wildfires previously occurred infrequently, but with high severity, our past suppression of wildfires often makes little difference.

In contrast, many California forests previously experienced more frequent, low-intensity fires. In these forests, fire suppression may greatly affect future fire risk, which the researchers point out underscores the urgency of restoration and fuels reduction - exactly the projects the Healthy Forests Act calls for - to reduce both community fire risk and the ecological impacts of climate change.

If nothing is done, global warming will have profound consequences for the future of our planet. Action must be taken now to reduce our greenhouse gas emissions. But even if prompt action is taken, the consequences of global warming will be with us for years. This is because carbon dioxide, once emitted, stays in the atmosphere for 50 years or more.

What this means is that our forests will remain at risk of catastrophic wildfire for a long time to come, both from global warming and from historical fire suppression. The Healthy Forests Act is the right strategy to reduce that risk in California's forests. But for long-term success in this battle, our nation must also be prepared to take dramatic steps to reduce global warming.