Our planet is undergoing dramatic changes right before our eyes. I am concerned about the connection these changes have with climate change, and I believe we can’t ignore the evidence or climate change science any longer. Misinformation and political debate surround this topic, despite consensus among respected scientific societies including the American Meteorological Society, the U.S. National Academy of Sciences and the Intergovernmental Panel on Climate Change (IPCC). To better understand the current phenomena and to better analyze climate-related headlines, let’s start by looking at the basic science of how our planet’s climate works.
Climate Change Science
The sun provides the solar radiation required for Earth to maintain a stable, life-supporting temperature. Solar radiation is cyclical; it stops at night. Earth’s atmosphere contains greenhouse gases (carbon dioxide, methane, nitrous oxide and water vapor), which help maintain the planet’s stable temperatures. These greenhouse gases cloak Earth like a blanket and allow shortwave radiation from the sun to pass through the atmosphere and warm the planet. They also absorb some of Earth’s outgoing radiation and then reradiate some of this absorbed energy — which would otherwise be sent into outer space — back to the Earth’s surface. Without the right mix of greenhouse gases, Earth would be too cold to support life.
Increased concentrations of greenhouse gases are now causing the planet to get warmer. This current warming is primarily the result of human actions, especially the release of carbon dioxide when humans burn carbon-based fossil fuels (coal, oil and natural gas). The extraction, processing and burning of fossil fuels has created an atmospheric overload of greenhouse gases.
Humans started using fossil fuels as an energy source during the Industrial Revolution. Before then, atmospheric levels of carbon dioxide were about 285 parts per million (ppm). In 2009, the level reached 390 ppm — substantially higher than any time in the past 800,000 years. (See the climate change chart in the Image Gallery.) Since 1850, Earth’s surface temperature has risen 1.3 degrees Fahrenheit, and the 20th century was warmer than any time period in the past 400 years.
The Effects of Climate Change
Climate change is not just about rising temperatures. It is also about other rapid changes happening now. Unless we make drastic adjustments, these changes will make Earth a more hostile place to live. What follows are the signs that climate change is already affecting the planet we live on, and the changes we can expect if global warming continues unchecked.
Sea Level Rise
Rising sea levels are due to thermal expansion of ocean water and melting of continental ice, primarily in Greenland and western Antarctica. The global rate of ice loss since 1990 is more than double the rate of the previous 30 years.
In the past 3,000 years, mean sea level rose 0.4 to 0.8 inches. But due to global warming, during the 20th century alone, mean sea level rose 8 inches. On a beach with a gentle slope of 1 degree, this 8-inch increase would move the shoreline inland almost 40 feet, leaving low-lying areas more vulnerable to floods and hurricane damage.
If we continue our current rate of fossil fuel use, scientists predict sea level will rise at least 3 feet by the end of the 21st century. Globally, more than 100 million people live less than 3 feet above sea level. Coastal plains, such as those along the Atlantic Ocean and the Gulf of Mexico, are at the highest risk, along with the major river deltas such as that of the Mississippi River. Henry Pollack, a geophysicist at the University of Michigan, points out that if we don’t slow climate change now, climate refugees will make our current immigration complexities seem like a Sunday school picnic.
Arctic Ice Melt
Historically, floating summer ice in the Arctic Ocean has covered an area about the size of the United States. This ice reflects the sun’s radiation and keeps the Arctic cool. But when sea ice melts away, the dark sea absorbs the sun’s radiation, which increases the water temperature, triggers more melting and raises the Arctic’s atmospheric temperature. Because of this feedback loop, within only a few decades, the Arctic Ocean could be ice-free in the summer for the first time in 55 million years.
Because of global warming and higher ocean temperatures, scientists report that plumes of methane (natural gas) are now rising from the Arctic Ocean. As long as it remains cold and under enough pressure, methane is stably stored in the ocean floor, and some estimates suggest there is more methane in the ocean floor than in all of Earth’s fossil fuel reservoirs. But signs that this methane is being released hold serious implications for our planet’s atmosphere, because methane is 20 to 25 times more potent than carbon dioxide as a heat-trapping greenhouse gas.
Warm air rising from the Arctic Ocean to arctic land masses triggers the melting of permafrost, a concrete-like combination of frozen water, soil and vegetation. Permafrost extends over about 20 percent of the planet’s land surface (mainly in the subarctic and arctic regions of North America, Asia and Europe) and can be up to 4,900 feet deep. When permafrost melts, it also releases methane into the atmosphere and causes land surfaces to collapse — toppling buildings and buckling roads. This melting also pushes more fresh water into the ocean, decreasing the sea’s salinity.
Mountain Glacier Melt
Mountain glaciers are rapidly disappearing, straining supplies of glacial water needed for agriculture, drinking water, sanitation and hydropower generation. The meltwater from the Himalayan and Tibetan Plateau glaciers, for example, provide fresh water for the people of India, China and most of Southeast Asia. One of the principal glaciers feeding the Yangtze River in China has retreated more than half a mile in just over a decade.
In the northwestern United States, much of the fresh water comes from the rapidly disappearing glaciers of Mt. Rainier, the Cascade Range and Glacier National Park. Grinnell Glacier, in Glacier National Park, has experienced a drastic, rapid recession. In 1850, Glacier National Park had 150 glaciers. Today it has 25.
As they grow, trees remove carbon dioxide from the atmosphere through photosynthesis and store an enormous amount of organic carbon. Deforestation caused by forest fires reduces photosynthetic activity — which results in the atmosphere retaining higher levels of carbon dioxide — and speeds the release of the carbon stored in the trees into the atmosphere as carbon dioxide.
Every degree increase in the temperature of the western United States brings roughly a 6 percent increase in lightning strikes. In June 2008 alone, lightning strikes triggered 1,700 forest fires in California, resulting in millions of burned acres.
In the past, deep winter freezes controlled the populations of many destructive insects. Now, winters are short and mild enough for the larvae of the pine bark beetle, as one example, to overwinter farther north. This beetle has destroyed more than 35 million acres of forest in British Columbia, Montana, Wyoming and Colorado, has recently crossed the Continental Divide into the forests of Alberta, and is heading toward the Great Lakes, leaving behind dead trees that fuel yet more forest fires.
Another example is the mosquito, which now enjoys an extended geographic range thanks to higher global temperatures. Mosquitoes harbor disease-causing viruses such as dengue fever, malaria and West Nile virus. Warmer weather means more mosquitoes bite more people and animals in more places around the globe, resulting in more cases of these diseases. El Salvador alone reported 22,000 cases of dengue fever in 2008, 20 times the number in 2003.
In recent years, we have seen increased numbers of hurricanes, more severe winter weather, massive floods, heat waves and droughts throughout the world. While weather is not a direct indication of climate change, the accumulating increase in severe weather signals an overall climate shift that’s creating powerful storms more frequently. (Read more on how climate change relates to weather events.) As sea levels rise and global atmospheric temperatures rise, more devastating weather events will occur — especially in low-lying areas and riparian flood plains — taking a greater financial and emotional toll on society.
Everything in our lives is ultimately tied to climate — where we live, water supply, food production, health and even national security. As changes begin, they trigger feedback loops that advance climate change at faster and faster rates. The Intergovernmental Panel on Climate Change, the international research authority on global warming, recently released its Fourth Assessment Report, declaring that the warming of Earth’s climate system is “unequivocal.”
How are we going to incorporate the effects of global warming into our lifestyle? How are we going to prevent further changes from taking place? We really have only two choices. We can continue business as usual and hope for the best, or we can end our current dependence on nonrenewable fossil fuels and move to a renewable energy economy with solar panels, wind turbines and geothermal systems. This will preserve the beautiful little spot in the universe we call home.
The United States has about 4 percent of the world’s population, but emits about 20 percent of the world’s carbon dioxide. If the shift to a renewable energy economy is to be successful, the United States must be the leader. The time to debate was yesterday. We must act today.
After a 34-year career as a research biochemist at Clemson University, Richard Hilderman, Ph.D., started studying climate change in 2007. Check out his blog, Understanding Climate Change.