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Almost 50 years after the first Earth Day in 1970, concerns about the “greenhouse effect” have evolved into fevered debates about global warming and climate change – heating up along with Earth’s overall temperature.

Each of the past three decades has been hotter than the one before, and yet the current White House administration has begun dismantling environmental policies meant to reduce carbon dioxide emissions that cause global warming. NASA reports that glaciers have shrunk, sea levels are rising, plant and animal ranges have shifted, and trees are flowering sooner as a result of climate change. The Bulletin of the Atomic Scientists recently set its Doomsday Clock 30 seconds closer to midnight – we are now at a metaphorical 2-1/2 minutes to global catastrophe – in part because the President and his environmental cabinet “dispute the basics of climate science.” We’re getting warmer, and not only because summer is on its way.

But Warm Winters Aren’t So Bad
 In spite of worldwide climate change anxiety, let’s admit we enjoyed the recent mild winter, which Illinois State Climatologist Jim Angel reports was the state’s fifth warmest on record. Winter 2016-17 saw lower than average snowfall (with no snow at all in January) and a string of shirt-sleeve days in February. And this isn’t new: three of the ten warmest Illinois winters have occurred since 2000, and seven have occurred since 1980. Even if Mother Nature delivers the blizzards and sub-zero temperatures that we consider normal in the midwest, warm winters appear to be the long-term trend. This must be proof positive of climate change! Well yes and no – because weather is different from climate.

“Weather is what we experience from day to day, and changing throughout the day,” explains Yarrow Axford, PhD, Associate Professor at Northwestern University’s Department of Earth & Planetary Sciences.

“Climate is weather averaged over decades.”

And even longer. Dr. Axford studies lake sediments to reconstruct Earth’s climate history over the last few thousand years – a time period when Earth was very similar to today but humans did not have the same impact on the planet as we do now.

Dr. Axford offers another take on the climate-weather difference: “Climate is what you expect and weather is what you get.” We expect cold, snowy weather every year, so after a heat wave in February or a record warm winter, people naturally ask whether climate change is responsible. But that is a difficult question to answer, Dr. Axford says, because global warming is changing what we expect and what we get.

“It’s creating a long-term trend toward a warmer planet, and that means that we can expect to see more heat waves and more warm days in the winter,” she explains. Such anomalies are consistent with what the world will be like in a warmer climate, but one specific weather event – a big storm or heat wave, for example – is not strictly the result of climate change. “What we can say is the odds of an event like that happening have gone up due to a long-term trend toward a warmer climate,” she says. (Watch how walking a dog illustrates climate vs. weather: tinyurl.com/climate-weather-dogwalk)

A Few Degrees of Change
In their Fifth Assessment report from October 2014, the Intergovernmental Panel on Climate Change (IPCC) – which was established by the World Meteorological Organization and the United Nations to assess the science of climate change – reports that:

• each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850
• the period from 1983 to 2012 was likely the warmest 30-year period of the last 1,400 years in the Northern Hemisphere
• the globally averaged combined land and ocean surface temperature shows an increase of about 1.4°F from 1880 to 2012.

Which sounds puny – less than two degrees warmer in 130 years. But a few degrees of global temperature change has always been associated with marked changes in sea levels, glacier activity, and ecosystems, Dr. Axford explains. Around 125,000 years ago, the average temperature measured 2°F to 3.5°F warmer than it is today – comparable to the amount of warming predicted for the end of this century. The warmer global temperature back then caused dramatic polar ice melt which shifted global sea level somewhere between 15-20 feet higher than it is today. That same sea level now would flood many U.S. coastal cities, including most of Miami, New Orleans, Savannah and Manhattan, according to the U.S. Geological Survey and National Oceanic and Atmospheric Administration.

A few degrees of cooling also accounts for significant climate differences, which the last ice age around 20,000 years ago made evident. “Chicago was covered by an ice sheet that extended all the way to the Arctic ocean,” Dr. Axford explains. “There would have been nothing to the north of us but ice a couple miles thick, and parts of Europe looked a lot like that, too.” Those extreme icy conditions prevailed when Earth’s global temperature measured just 7°F to 12°F cooler than it is today.

Drilling into Carbon History
Carbon dioxide (CO2 ) is largely responsible for those global temperature swings, and today’s atmospheric CO2 concentration exceeds levels recorded over the past 800,000 years, according to the IPCC. Scientists have been able to compile carbon dioxide data by tapping the Antarctic ice sheet for samples of ancient atmosphere trapped deep within. Ice sheets form when a mixture of snow and air compacts into layers of ice and air bubbles year after year, for hundreds of thousands of years. Researchers drill into ice sheets to extract long cylindrical ice cores so they can study the atmosphere preserved in those layers. They can literally stick a needle into the bubbles, draw out some trapped air, and measure the amount of CO2 present in the atmosphere during various time periods.

“That carbon dioxide record is something we have a high level of confidence in,” Dr. Axford says. “It’s a very direct measurement of what the atmosphere was like.” Because CO2 in Earth’s atmosphere mixes globally, a carbon dioxide measurement representing a year over Antarctica at a given time in history would be the same as a measurement from the same year anywhere else on the planet, she explains. So ice core samples help climate scientists reconstruct a deep and accurate global carbon dioxide record.  (Take a few minutes to see how dramatically CO2 levels have changed over the past 800,000 years: tinyurl.com/co2-history.)

Earth Day Matters
As Earth Day approaches, it is tempting to lose hope for our ever-warming planet’s future. After all, what good is a day originally created to put the environment on the national political agenda when politicians keep trying to take it off, when damaging CO2 levels keep going up, and both climate and weather are changing for the worse. But Denis Hayes, an environmental activist who organized the first Earth Day, maintains that the day is just as relevant now as it was five decades ago.

“One day by itself does not transform the human prospect,” admits Mr. Hayes, now President and CEO of the Bullitt Foundation, which promotes environmental protection and sustainable development in the Pacific Northwest. “However, such days do provide a focal point each year to celebrate accomplishments and assess how we are doing.”

Mr. Hayes points out that every Earth Day provides an opportunity for people to celebrate environment-oriented successes and announce new goals for the future. Schools and universities often unveil new solar energy systems or open organic gardens. World leaders met on Earth Day 2016 to execute the Paris Climate Accords. And the March for Science takes place in Washington, D.C. this Earth Day – an event which Mr. Hayes says will “protest the Trump Administration’s defunding of basic research, its censorship of scientific research, and its reliance on ‘alternative facts’ to set national policy.”

Closer to home, community members can help clean up parks and public spaces during the city’s annual Earth Day and Arbor Day event called “Clean up, Evanston!” ETHS and the Kiwanis Club are coordinating clean up efforts around the high school, and the City will also hold a tree planting ceremony in front of the Morton Civic Center.

The Dawning of the Age of Environmentalism
“The first Earth Day in 1970 was fueled by the same optimism and idealism that propelled the anti-war movement and the civil rights movement,” says Mr. Hayes. “We were mostly very young and we were all absolutely confident we would pass on a better world to our children than the one we had inherited.” Back then, Earth Day centered around issues such as air and water pollution, new freeways threatened to destroy vibrant neighborhoods, cancer-causing defoliants used in the Vietnam war, leaded paint and gasoline, pesticide and herbicide abuse, protection of parks and natural areas. And by year’s end, Congress approved a proposal to create the Environmental Protection Agency (EPA).

Since then, Earth Day has gone international, with an estimated one billion people from almost 200 countries celebrating what Mr. Hayes describes as the “largest secular observance in the world.”

Mr. Hayes cites climate change, ocean acidification, and endangered migratory species as some of today’s key environmental concerns – issues that may seem remote and require global cooperation.  It is harder to mobilize people around those issues because they are more concerned about immediate threats to their children or their neighborhoods, he says. America is also more polarized today, economically and politically. And he makes no secret about his feelings toward the Trump administration’s position on the environment.

“When the President cavalierly shreds international agreements that thousands of people worked for decades to produce, it
is disheartening and infuriating,” Mr. Hayes says.

We Opened This Can of Worms
Although Mr. Hayes applauds the progress made on environmental problems like air pollution since the first Earth Day, scientists continue to mount evidence that human-generated CO2 is warming the climate and altering weather patterns. As a consequence, global sea levels will continue to rise and the Greenland ice sheet will keep shrinking, but the magnitude of those changes is still uncertain. Dr. Axford hopes research like hers on past climate change will help us better understand how quickly the globe as a whole will respond to climate change going forward. And humans need to take responsibility.

“We know from work that climate scientists have done over decades that humans are changing Earth’s climate,” she says. “What we don’t know is exactly how fast anything will change, and exactly how large the changes will be. I’d like people to acknowledge that we live on a changing planet, that humans are causing that change, and that we understand the problem as much as we can.”

Meg Evans

Meg Evans has written science stories for the Evanston RoundTable since 2015, covering topics ranging from local crayfish, coyotes and cicadas to gravitational waves, medical cannabis, invasive garden...