What can we do about global warming?

By UCAR (Univercity Corporation for Atmosphere Research)

There are two basic types of response to climate change. Mitigation is reducing the emissions of greenhouse gases responsible for climate change, so that less change occurs. Adaptation is dealing with the consequences of warming and other aspects of climate change, such as changes in extreme weather events.

Because some amount of climate change has already occurred, and more change is inevitable based on the greenhouse gases already emitted, society will need to adapt. Yet in order to prevent even more-extreme climate change from happening, mitigation will be required.

Policymakers are now examining these two types of responses, including how much attention and what resources to devote to each one and how to find a balance between mitigation and adaptation.

"Business as usual" is also a choice. This option saves expenditures for mitigation in the near term, but risks higher adaptation costs to wildlife, human populations, infrastructure, and economies later on. It also increases the odds of unforeseen consequences from unchecked climate change.

The 2007 IPCC report helps policymakers weigh these options. To promote discussion of policy choices in our democracy, NCAR's parent organization, UCAR, has joined with professional societies and other members of the atmospheric sciences community to offer policy-relevant Advice to the Administration and Congress: Making Our Nation Resilient to Severe Weather and Climate Change.

As impacts on natural systems are being felt, human adaptation is already happening on some fronts. Many insurance companies are examining their practices and taking climate change into account in setting their rates and their policies. Air conditioning is becoming more widespread in North America and Europe. Some communities on small islands are already making plans to abandon their homes due to rising sea levels. The fate of plants and animals that cannot readily adapt is being discussed.

The United States joined with many other nations in signing a treaty in 1994 known as the United Nations Framework Convention on Climate Change. The UNFCCC, which has been ratified by 192 countries, recognizes that the climate system has no boundaries and that international cooperation is needed to seek solutions to the problems posed by rising greenhouse gases.

Considered a first step in a long diplomatic process, the Kyoto Protocol was an early and well-known agreement that emerged from the UNFCCC process. The protocol, which set modest targets for reducing greenhouse gas emissions, was adopted in 1997 and ratified by most countries in the world, though not the United States and Australia. Its targets have been in force for over 180 signatory nations since early 2005. NCAR scientist Tom Wigley's research has shown that adherence to the Kyoto Protocol alone, without subsequent action, would have a minimal impact on global warming. However, he notes, "This does not mean that the actions implied by the Protocol are unnecessary."

An important UNFCCC meeting took place in 2009. The 15th Conference of the Parties to the UNFCC, or COP 15, met in Copenhagen, Denmark, December 7–18, to focus on mitigation and adaptation strategies beyond the Kyoto Protocol, which is set to expire in 2012.

Many U.S. cities and states have committed to reducing their output of greenhouse gases over the coming decades. Mitigation is also happening on the personal level (buying a fuel-thrifty or hybrid vehicle, for instance, or installing energy-saving light bulbs) and in private industry (a growing number of businesses and organizations have pledged to become carbon neutral).

Volunteer "citizen scientists" are recording their observations to provide information about our climate over time. Some researchers are tapping a rich historical record of bird migration and seeking new volunteers to report migration arrivals and departures. A collaboration between public and private agencies hosted by UCAR's Windows to the Universe encourages volunteers to report the timing of budburst in spring. Participants record when dormant plants produce leaves and their flower buds first open in response to climate signals.

What is the green house effect?

By UCAR (Univercity Corporation for Atmosphere Research)

Without the so-called greenhouse gases, including carbon dioxide, methane, nitrous oxide, and water vapor, Earth would be too cold to inhabit. These gases in Earth's atmosphere absorb and emit heat energy, creating the greenhouse effect that keeps our planet's temperature livable.

Water vapor is the most plentiful greenhouse gas on the planet, accounting for about 60% of the current greenhouse effect. Even ozone helps trap some of the heat that makes life on Earth possible, but the "ozone hole" is a separate issue not directly related to global warming.

Color visualization of the greenhouse effect

Watch a 1-minute animation on the greenhouse effect. Click here or on the image to launch in a new window (streaming video).

Too Much of a Good Thing

Since the industrial revolution, people have burned vast amounts of coal, petroleum, and other fossil fuels to create heat and power. This releases carbon dioxide, the most plentiful human-produced greenhouse gas, into the atmosphere. The result: more heat is trapped in Earth's atmosphere instead of radiating out into space.

Because carbon dioxide lasts more than a century in the atmosphere, it is well mixed around the globe. Measurements collected atop Hawaii’s Mauna Loa since 1958 show a steady rise in global carbon dioxide concentrations. These have increased by 35% since preindustrial times, according to the World Meteorological Organization. Other, less prevalent greenhouse gases have increased at different rates. Methane, for example, has virtually leveled off since 1999 at 155% above its preindustrial level.

The relationship between Earth's water cycle and global warming creates a well-known feedback loop. Warmer temperatures cause more evaporation from land and oceans, which produces more water vapor, which in turn contributes to warmer temperatures. This is just one of many feedbacks in the Earth system that climate scientists are studying to improve projections of future climate change.

What Is Global Warming?

The Planet Is Heating Up—and Fast

by National Geographic

Photograph by Paul Nicklen

Glaciers are melting, sea levels are rising, cloud forests are drying, and wildlife is scrambling to keep pace. It's becoming clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than in the last 650,000 years.

We call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. As the Earth spins each day, the new heat swirls with it, picking up moisture over the oceans, rising here, settling there. It's changing the rhythms of climate that all living things have come to rely upon.
What will we do to slow this warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the face of the Earth as we know it—coasts, forests, farms and snow-capped mountains—hangs in the balance.
Greenhouse effect
The "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse.
First, sunlight shines onto the Earth's surface, where it is absorbed and then radiates back into the atmosphere as heat. In the atmosphere, “greenhouse” gases trap some of this heat, and the rest escapes into space. The more greenhouse gases are in the atmosphere, the more heat gets trapped.
Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the Earth would be much colder if it had no atmosphere. This greenhouse effect is what keeps the Earth's climate livable. Without it, the Earth's surface would be an average of about 60 degrees Fahrenheit cooler. In 1895, the Swedish chemist Svante Arrhenius discovered that humans could enhance the greenhouse effect by making carbon dioxide, a greenhouse gas. He kicked off 100 years of climate research that has given us a sophisticated understanding of global warming.
Levels of greenhouse gases (GHGs) have gone up and down over the Earth's history, but they have been fairly constant for the past few thousand years. Global average temperatures have stayed fairly constant over that time as well, until recently. Through the burning of fossil fuels and other GHG emissions, humans are enhancing the greenhouse effect and warming Earth.
Scientists often use the term "climate change" instead of global warming. This is because as the Earth's average temperature climbs, winds and ocean currents move heat around the globe in ways that can cool some areas, warm others, and change the amount of rain and snow falling. As a result, the climate changes differently in different areas.
Aren't temperature changes natural?
The average global temperature and concentrations of carbon dioxide (one of the major greenhouse gases) have fluctuated on a cycle of hundreds of thousands of years as the Earth's position relative to the sun has varied. As a result, ice ages have come and gone.
However, for thousands of years now, emissions of GHGs to the atmosphere have been balanced out by GHGs that are naturally absorbed. As a result, GHG concentrations and temperature have been fairly stable. This stability has allowed human civilization to develop within a consistent climate.
Occasionally, other factors briefly influence global temperatures. Volcanic eruptions, for example, emit particles that temporarily cool the Earth's surface. But these have no lasting effect beyond a few years. Other cycles, such as El Niño, also work on fairly short and predictable cycles.
Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the industrial revolution. Changes this large have historically taken thousands of years, but are now happening over the course of decades.
Why is this a concern?
The rapid rise in greenhouse gases is a problem because it is changing the climate faster than some living things may be able to adapt. Also, a new and more unpredictable climate poses unique challenges to all life.
Historically, Earth's climate has regularly shifted back and forth between temperatures like those we see today and temperatures cold enough that large sheets of ice covered much of North America and Europe. The difference between average global temperatures today and during those ice ages is only about 5 degrees Celsius (9 degrees Fahrenheit), and these swings happen slowly, over hundreds of thousands of years.
Now, with concentrations of greenhouse gases rising, Earth's remaining ice sheets (such as Greenland and Antarctica) are starting to melt too. The extra water could potentially raise sea levels significantly.
As the mercury rises, the climate can change in unexpected ways. In addition to sea levels rising, weather can become more extreme. This means more intense major storms, more rain followed by longer and drier droughts (a challenge for growing crops), changes in the ranges in which plants and animals can live, and loss of water supplies that have historically come from glaciers.
Scientists are already seeing some of these changes occurring more quickly than they had expected. According to the Intergovernmental Panel on Climate Change, eleven of the twelve hottest years since thermometer readings became available occurred between 1995 and 2006.