Climate surrounds us from the day we’re born until the day we die.

Yet, unless you’re being pounded by a nor’easter or broiled in a heat wave, it fades into the background of catching that bus, making that call, getting dinner to the table on time.

It’s all too easy to forget that changes in Earth’s climate and the wild weather patterns that follow can wipe away our narrow worlds in an instant.

This is a world where a dust storm in the Sahara can darken Miami’s golden coast. It’s a place where a volcanic eruption in Southeast Asia can usher in cold weather to steal a summer from Americans, where water from a melting glacier in Antarctica can swamp an island in the South Pacific.

While we slog through the fog of our daily lives, the rain, the heat, the oceans and the air we breathe are in constant communion, precisely calibrated in ways scientists still don’t completely understand.

Climate always has changed, and it always will.

As Paul Mayewski, director of the University of Maine Climate Change Institute, likes to say,

“You can’t escape climate.”

No single cause, no simple answer

Most Mainers have heard of global warming, but the truth of the Earth’s changing climate is far more complex than a simple equation of pollution equals warmer weather.

“The Earth’s climate is not a black-and-white system. It’s many shades of gray,” said Greg Zielinski, Maine’s state climatologist and a Bangor resident.

The vast majority of the world’s scientists don’t doubt that there is an out-of-control greenhouse effect occurring, in which pollutants such as carbon dioxide and methane build up in the atmosphere, trapping unnatural amounts of heat from the sun near the Earth’s surface.

“It’s very clear that the greenhouse gases are part of this story,” said Robert Kates of Trenton, a member of the National Academy of Sciences who has helped craft international reports on climate change.

But answering the question of just how large a part human activities such as burning fossil fuels and cutting down forests play in determining the Earth’s climate will require solving one of the most staggering problems ever considered by humankind: How does the world work?

Just as an orchestra needs dozens of different instruments, each playing its role, to perform all the dips and swells of a symphony, climate is more complicated than it first appears.

Solar flares – often cited by detractors as evidence to discount the theory that climate change is caused by humans – play an important role, perhaps prompting climate cycles on a time scale of tens of thousands or even hundreds of thousands of years. But also playing a part are the “wobbles” in the Earth’s rotation around the sun and the shifting locations of the continents.

Over shorter periods, dramatic natural events such as volcanic eruptions and changing ocean currents can transform the climate, both locally and worldwide. Hundreds of factors, some of which scientists are just beginning to observe, have influenced the melody of climate over the eons.

“Discounting that anything else happens, there would be that nice, simple relationship [between atmospheric carbon dioxide concentrations and global temperatures]. But other things do happen,” said Kirk Maasch, a climatologist at the University of Maine.

That makes linking the pollution coming out the tailpipe of your neighbor’s sport utility vehicle to your earlier-blooming lilacs absolutely impossible.

“We can never say that a single event, a hurricane or a flood or a warm season, is caused by greenhouse gases,” said University of Maine paleobotanist George Jacobson.

Climatologists graph out the cycles they recognize, each line atop the last like hundreds of echocardiograms, until clear peaks and valleys emerge.

“All of it comes into play,” Maasch said. “You’ve got to keep [all the factors] in and let the cards fall where they may,” he said.

A gumbo of disciplines

But even the best climate records from Arctic ice cores go back only about 100,000 years, while most scientists today believe that the Earth was formed at least 4.6 billion years ago.

As science essayist John McPhee once wrote, imagine a man standing with both arms outstretched as a timeline. If the tip of the left middle finger represents the birth of the planet, then the whole of human civilization – just 10,000 years – is encompassed in the fingernail of the right middle finger.

While the concept of a warming climate caused by excess carbon dioxide and other greenhouse gases in the atmosphere dates back to the 19th century, it wasn’t until the environmental movement of the 1960s that the idea captured people’s imaginations. Talk of mass pesticide poisonings and potential nuclear winter brought home the possibility that humans could change the entire world, Kates said.

For thousands of years, the El Nino cycle in the Pacific and the devastating storms that marked the start of a cold period called the Little Ice Age nearly 700 years ago were attributed to the supernatural, a punishment from above.

Today, climate is the provenance of scientists, not philosophers, although this gumbo of disciplines – incorporating geology, biology, oceanography, chemistry and, increasingly, social sciences such as history and archaeology – requires more than a little faith.

Mayewski travels the world, saving ice cores from rapidly melting glaciers in hopes that they can reveal the history of the world. Other scientists hunt messages in rock formations. Jacobson seeks knowledge in ancient pollen trapped far beneath lake waters. Each believes that the information is there, waiting to be tapped.

“It’s not a simple matter of one kind of evidence telling the whole story,” Jacobson said. Only from all these stories from ice cores, lake sediments, fossils, tree rings, coral reefs, rocky cliffs and even old diaries will a full picture of the past emerge.

“The data becomes so diffuse and broad and plentiful that one person can’t handle it all,” said Harold “Hal” Borns, professor emeritus at the University of Maine and a founder of the multidisciplinary Climate Change Institute.

“All the knowledge just can’t be locked up in one or two people,” Borns said.

At the University of Maine, one of several centers for climate research around the country, scientists are piecing together the history of the natural world in hopes of someday being able to predict the sorts of drastic changes that affected the planet long before our cities were built and that very likely will happen again. And once the natural systems are defined, the role that we play in transforming the climate will become clear, Jacobson said.

“It’s only in understanding the natural variability that we can see what’s happening today,” he said.

‘We’re still in the ice age’

Mainers joke about the brevity of a New England summer, claiming that all they have to do is blink once and the snow is falling again. But warm periods of time in which the state experiences anything that can be called a summer have been tremendously rare – just 10,000 years of heat for every 100,000 years of snow.

The Earth is still in the throes of an ice age, a period of alternating warm and cool phases that began half a million years ago.

“We’re still in the ice age, and most people don’t know what the ice age is,” Borns said.

The woolly mammoths that once marched over the sheets of ice atop what is now Bangor are long gone, but millions of years of climate data indicate that the world may be poised on the edge of the next glaciation, or cool phase of the ice age. Of course, to climate scientists, who think on mind-boggling time scales, that edge could last for many human generations.

“Some people say we’re 500 to 1,000 years overdue,” Borns said. “We’ve been through the warm spell.”

Four times over the past 500 millenniums, ice has advanced, as though on a regular schedule. The most recent glaciation, which ended between 12,000 and 17,000 years ago, formed Maine’s landscape. Glaciers scraped over the rocky ground, chiseling the peaks and valleys of Baxter State Park and the White Mountains.

Then, as the ice receded, melting water rushed over the land, leaving long, narrow deposits of sand and gravel that snake across the state.

“Over a period of just 4,000 or 5,000 years, there was an incredibly rapid change from Maine being covered by ice to being covered by forest,” Jacobson said.

Climate can evolve over millions of years or bring drastic change in as little as two years. Some scientists believe that, if not for the part of global warming caused by humans, the globe might have remained in a cooler phase or even slipped into a more permanent freeze.

The fact remains that, by some estimates, the Earth’s average temperatures are higher than at any other point in the last 400,000 years, said Kates.

“It’s the hardest question in the world: How do you recognize change when you’re in the middle of it?” he said.

‘What are the consequences?’

Four hours up the face of Hamlin Peak in Baxter State Park, a hiker is rewarded with a glimpse of what could be lost if Maine’s climate is, in fact, warming.

Tiny denizens of the tundra are clustered along the trail not far from Baxter Peak, the state’s mile-high apex. Alpine bilberry, mountain cranberry and diapensia crawl across the bare granite boulders.

Bigelow’s sedge and Labrador tea grow in mountaintop meadows where the Katahdin Arctic butterfly, an invertebrate on the state’s endangered species list, lives its few weeks – the only place in the world where this subspecies is known to breed.

Each of these organisms lives in one of the harshest climates Maine has to offer, yet they could be the first victims of a warming climate. As temperatures rise, alpine plants migrate to higher altitudes, but as they run out of habitat near the peaks, Katahdin’s rare species could simply disappear. Volunteers from the Appalachian Mountain Club are keeping a close eye on their populations.

Meanwhile, all across the world, flowers are blooming earlier, songbirds are sticking around through the fall, and glaciers are melting away.

“What we’re doing now is a global story,” said Jacobson, referring to humanity’s role in climate change. “We’re changing the whole chemistry of the Earth in a way that’s going to have consequences.

“We’ve already changed the atmosphere,” he said. “The question is: What are the consequences of all that heat?”

Between 1895 and 1999, New England’s average temperature increased by 0.7 degrees Fahrenheit. Data from Maine over the past century show that temperatures are rising in the southern third of the state, holding steady in the central regions and dropping slightly in the north.

“What people want to know is: ‘How is it going to affect them?’ But that’s the hardest thing,” said Zielinski, the state climatologist. “Maine is tough, because we are at a zone of climate boundaries,” he said. “It’s not an easy place to forecast.”

Climatologists have used historical data and weather observations from recent centuries to build models or computer programs that predict climate change.

Some day these models may be able to foresee droughts and anticipate floods.

But today there isn’t enough data to paint a precise view of the future. Some climate models predict a wetter Maine, some drier. Major models forecast that New England’s temperature could rise somewhere between 6 and 10 degrees in the next century. At the extreme end, such a change would transform Boston’s winters to something akin to Atlanta today.

Even if the exact impacts of climate change can’t be defined, clearly something is happening. The Pentagon was concerned enough about drastic climate change that in 2004, officials issued a report warning of war and famine.

Despite lingering questions about what the exact consequences may be, one thing is clear: Interfering with a complex natural system that we don’t yet understand is irresponsible, Kates said.

“The evidence keeps piling up more and more,” he said. “How can we play dice with the planet?”