What is the best source of scientific information on global warming?

The IPCC’s Third Assessment Report is the most comprehensive and up-to-date evaluation of global warming. It serves as the basis for international climate negotiations. The Intergovernmental Panel on Climate Change (IPCC) was established in 1988, by the United Nations Environment Program and the World Meteorological Organization. It includes more than 2,500 of the world’s leading climate scientists, economists, and risk experts who have contributed to the panel’s most recent report, Climate Change 2001: The Third Assessment Report. Scientists from about 100 countries were involved in this writing this report, reviewed all the published and peer-reviewed scientific information produced during the previous few years and assessed what is known about the global climate.

Isn’t there still a lot of debate and uncertainty?

The heat-trapping properties of global warming pollutants are undisputed. The fact that human activities generate these global warming pollutants is also undisputed. With more than 15 years of observed and studied scientific data, we now understand the climate system and its relationship to human activities. There is consensus among the IPCC and scientists about the reality of global warming. Although there may be uncertainty about exactly when, where and how the earth’s climate will respond to global warming pollutants, there is no dispute, and observations indicate, that detectable warming changes are already under way.

Myth: Science is wrong/ Global warming is not real.

According to data presented by the Climatic Research Unit, the last three decades (1976-2005) have seen a sharper rise in global air temperature than any other period since at least 1860. Increases in temperature and changes in precipitation, soil moisture, and sea level, could have adverse effects on many ecological systems, as well as on human health and the economy.

How do we know if Global warming is a natural phenomenon vs. human-made one?

IPCC experts have concluded that there is human influence on the global climate. Human activities are adding global warming pollutants at an unprecedented rate. The burning of fossil fuels — coal, oil, and natural gas — is the primary source of power generation, and burning these fuels adds global warming pollutants to the atmosphere. The fuels burned to run cars and trucks, to heat homes and businesses, and to power factories, are not natural phenomenon. Agriculture, deforestation, landfills, industrial production and mining, are other human activities that also contribute to global warming pollutants. Human activities account for ~80% of global carbon dioxide emissions.

Aren’t there a lot of other factors responsible for global warming?

Natural and human factors can both affect the average temperature of our planet. Natural variability in the Earth’s climate system can cause small changes over decades to centuries. Industrialization has increased that rate, so that 80% of the current global carbon dioxide emissions result from human activities. In the 21st century, the global warming pollution that humans are causing will impact the climate tens or possibly a hundred times faster than natural rates

I’ve heard that satellite data contradict other evidence of global warming.

Scientists recently discovered that they neglected some measurement and calibration problems with the satellites, including the fact that the satellites were falling from their orbits, which produced an artificial cooling trend. Correcting the satellite data for these problems brought the satellite data into better agreement with surface measurements and revealed a warming trend.

I’ve heard that the United States advisors have data that contradicts evidence of global warming?

In 2000, Frank Luntz famously penned a memo that recommended ways for President Bush and his allies to discuss global warming in a manner that cast doubt on the science. Among his suggestions, Luntz recommended the following key point: The Scientific debate remains open: voters believe that there is no consensus about global warming withit the scientific community. Should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly. Therefore you need to continue to make the lack of scientific certainty a primary issue in the debate, and defer to scientists and other experts I the field. Since this time, the author himself has backed away from his advice, believing the scientific issues are now settled: I think most people would conclude that there is global warming taking place, and that the behavior of humans are affecting the climate. In addition, it is important to know that the Bush administration has in fact taken a position on climate change: In February 2002, the United States government announced a comprehensive strategy to reduce the greenhouse gas intensity of the American economy by 18 percent over the 10-year period from 2002 to 2012. www.epa.gov/climatechange. The agency supports a number of programs aimed at reducing green house gas emissions.

Myth: I’ve heard that even the National Academy of Science (NAS) disputes global warming! The experts cannot even agree!

There was a 1975 study by the U.S. National Academy of Sciences that did not deny nor did it make predictions. It simply stated: “we do not have a good quantitative understanding of our climate machine and what determines its course. Without the fundamental understanding, it does not seem possible to predict climate.”They called for further research, because “it is only through the use of adequately calibrated numerical models that we can hope to acquire the information necessary for a quantitative assessment of the climatic impacts.” Today we have those calibrated models. In 2003, NAS stated: “Over the next century it is likely that forcing of the climate system by human activities will greatly exceed changes caused by natural events”. And in their latest report, June 2005, the NAS states: “The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action”.

I thought there were 1700 scientists who signed a petition that disputed global warming?

A petition sponsored by the Oregon Institute of Science and Medicine (OISM) was circulated in April 1998 with what appeared to be a reprint of a scientific paper that was formatted to look as though it had been published by the National Academy of Sciences. NAS issued a public statement that the OISM petition did not reflect the conclusions of their experts. The actual author and the co-authors were not climate scientists. The author was a biochemist with no published research in the field of climatology, and his paper had never been subjected to peer review by anyone. Although the signatories did include a few reputable scientists, it also included dentists, nutritionists and others with no expertise in climatalogy; the only requirement for signing was a bachelors degree in science. In fact, OISM’s screening process was so lax that for a time the list also included : Donald Duck, Ginger Spice and Michael J. Fox!

Aren’t there always going to be unknowns? Science changes all the time, new studies, new findings, we never know what is next!?

Global warming specifics might not tell us exactly where, when and how– but the science is clear that we can no longer warrant a “wait and see”policy. Science tells us with increasing certainty that we are in for a serious long-term problem that will affect all of us. There are actions that make economic sense while helping to reduce our impact on the global climate and on our local environment and health. Developing new, clean, energy-efficient technologies can be done in a cost-effective manner, while creating jobs and new business opportunities.

If there are so many variables, how can you say that any one extreme weather event is a result of climate change?

Global climate requires a holistic approach. Attributing any particular extreme weather event to global warming remains beyond the current limits of scientific capability. However, given our knowledge of global warming and our changing climate, we know we can expect more extreme weather, including more frequent hot days and droughts, less frequent cold days, and more focused precipitation (including more snowfall in cold areas).

Myth: I saw a recent science show on Global freezing, and then there’s the movie: “Day after Tomorrow” that says we are going to also end up with a freeze in some areas—so won’t they just cancel each other out?

This theory gained temporary popular attention due to News reporting in the 1970’s. At that time they were trying to better understand ice age cycles and there appeared to be a temporary downward trend of temperatures. The theory never had strong scientific support. At present, the Earth is not considered to be cooling, but rather to be in a period of global warming mostly attributed to human activity.

Can’t we just wait? The GHG emissions are not rising at a very rapid rate—the rate should not cause concern or require us to act now.

Even the most conservative predictions in the IPCC’s report show rates of climate change unprecedented in the past 10,000 years. Since pre-industrial times atmospheric concentrations of CO2, CH4 and N2O have climbed by over 30%, 145% and 15% respectively. Scientists have confirmed this is primarily due to human activity. Human activities are now adding about 7 billion metric tons of carbon into the atmosphere each year. That’s enough to cause an imbalance, surpassing nature’s ability to take our added CO2 out of the atmosphere. Also, we need to consider that half of these emissions remain airborne for over a 100 years, causing the affect to accumulate. We are committing ourselves to a warmer climate in the future.

How much warmer is the Earth likely to become?

The IPCC’s Third Assessment Report projects that the Earth’s average surface temperature will increase between 2.5° and 10.4°F (1.4°-5.8°C) between 1990 and 2100 if no major efforts are undertaken to reduce the emissions of greenhouse gases.


Can’t we just wait and see if there are going to be more impacts?

Climate change is a challenge too important to be denied and too urgent to be ignored. As cities, we depend on materials, products and people everywhere, and, as such, we need to work together to manage our world. In the absence of action by the federal government, US mayors are confronting climate change and working to improve the quality and livability of our cities. . It isn’t so much what you do—just so long as you do it

Is it too late to avoid the impacts?

With concerted action, it is a challenge that can be overcome. Researchers such as University of New Hampshire earth science professor Cameron Wake, who tracks such phenomena as the earlier arrival of spring, sees a silver lining in this cloud. “This country is at its best when it has a grand challenge, whether it’s World War II or going to the moon,”Wake says. “This is the next grand challenge.”Our path is not cast in stone. Setting goals spurs innovation. Momentum is currently building for local solutions to climate change


Won’t this require lifestyle changes and inconveniences? i.e. more time to get places if I use public transportation, more expensive alternatives etc?

The overall long-term effect of change will be an improvement in lifestyles, quality of life and livable cities. The short term costs of purchasing biodiesel can be easily offset if we prevent increases in childhood asthma rates. Carpooling can cut down on commute time since it alleviates traffic congestion,pedestrian and bicycle friendly shopping areas generate a community center, and green power can provide fixed cost procurements.

Isn’t this expensive? We can’t afford to address climate change

We can’t afford NOT to address climate change. The potential economic costs of impacts such as flooding, drought, loss of forest and tourism, are enormous. Companies are finding that reducing emissions can actually improve operational efficiencies, reduce energy and production costs, and increase market share.

Won’t this hurt the economy?

Investing in energy efficiency can actually save you long term monies on your electric bills and extend the life of your equipment. Avoiding short term costs now could result in long term costs later. There is an economic risk of not responding early enough to avoid major negative (costly) impacts later. Technology is moving towards environmental investments and innovations. Making changes now can make you a leader in technology, generate new business, and create jobs in your community.

Isn’t this expensive? If it is so affordable why aren’t more cities doing it?

More and more cities are signing up and participating in programs every day. Cities across the US are now realizing that this makes good business sense.

Why sign up for more when we are doing so much already?

Cities benefit from tracking successful performance, and acknowledging achievements and attainment of goals with other city leaders. Sharing information, technologies and creative solutions brings economies of scale and will ultimately improve your bottom line.

How can small actions really make a difference to things happening on this epic scale?

Clearly, different regions and cities will have different approaches to reducing global warming emissions. But every piece, no matter how big or small, has an impact. Did you know that one old leaf blower can release as much pollution in one year as 80 cars? Replace city leaf blowers with cleaner, quieter, low-emission machines.

The market will take care of this; let the private sector lead.

The corporate sector won’t make major changes for the sake of public health and safety or to protect the environment unless it gets strong signals to do so. Local, federal and city government should send clear signals and provide supportive conditions that encourage businesses to invest in the development of new clean energy technologies and energy-efficient products.

The US is doing a lot already. Why can’t the other countries get involved and do their part?

In 1994, the United States emitted about one-fifth of the total global warming pollutants. It is up to the U.S. to do our part to be sustainable, and to strive to provide one-fifth of the targeted global warming pollution reductions.


Couldn’t global warming be beneficial?

The warming that humans are causing will warm the Earth’s climate at tens or possibly a hundred times faster than natural rates of climate change. Warming of a few degrees may appear minor compared to short term weather shifts, but in a global climate terms, this rate is faster than any climatic change that we’ve seen in 10,000 years. Warming of 2 to 6 degrees would lead to more frequent droughts and heat waves, cause greater rainfall and possibly change the strengths of storms.

But I’ve heard that CO2 helps plants and crops?

Yes, there are complex interactions with crops and vegetation. Although CO2 can essentially fertilize plants and crops, the plant is also affected by other factors that also result from more CO2—which is rising temperatures. The increase in global climate can increase the rate of evaporation, drying out soils. Insufficient water decreases plant growth. Plants in turn, cannot respond to more CO2 unless sufficient nutrients are available. Long term studies show that the growth-enhancing effects of CO2 may diminish over time. See EPA FAQ.

Links To Other FAQs