Are Humans Substantially Responsible for Global Climate Change Today?

General Reference (not clearly pro or con)
The Congressional Research Service stated the following in its June 25, 2007 report "The Carbon Cycle: Implications for Climate Change and Congress," available at its website:

"Carbon is stored in the atmosphere, in the oceans, in vegetation, and in soils on the land surface. Huge quantities of carbon are actively exchanged between the atmosphere and the other storage pools of carbon. The exchange, or flux, of carbon between the atmosphere, oceans, and land surface is called the carbon cycle. In sheer magnitude, human activities contribute a relatively small amount of carbon, primarily as carbon dioxide (CO2), to the global carbon cycle. Burning fossil fuels, for example, adds less than 5% to the total amount of CO2 released from the oceans and land surface to the atmosphere each year...

Humans tap the huge pool of fossil carbon for energy, and affect the global carbon cycle by transferring fossil carbon — which took millions of years to accumulate — into the atmosphere over a relatively short time span...

As the CO2 concentration grows it increases the radiative forcing (more incoming radiation energy than outgoing) of the atmosphere, warming the planet."

June 25, 2007 - Congressional Research Service (CRS) 
"The Carbon Cycle: Implications for Climate Change and Congress" (242KB)  

PRO (yes)

The US Environmental Protection Agency (EPA), discussed the human contribution to climate change in the following passage posted to its website (accessed July 8, 2008):

"Careful measurements have confirmed that greenhouse gas emissions are increasing and that human activities (principally, the burning of fossil fuels and changes in land use) are the primary cause. Human activities have caused the atmospheric concentrations of carbon dioxide and methane to be higher today than at any point during the last 650,000 years. Scientists agree it is very likely that most of the global average warming since the mid-20th century is due to human-induced increases in greenhouse gases, rather than to natural causes...

Natural variations within the Earth's climate system can cause small changes over decades to centuries... However, while natural variations have altered the climate significantly in the past, it is very unlikely that the changes in climate observed since the mid-20th century can be explained by natural processes alone."

July 8, 2008 - Environmental Protection Agency (EPA) 

The Intergovernmental Panel on Climate Change (IPCC), a scientific intergovernmental body set up by the World Meteorological Organization (WMO) and by the United Nations Environment Programme (UNEP), wrote the following in its Nov. 2007 summary of the report "Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change," available at

"Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land use change, while those of methane and nitrous oxide are primarily due to agriculture...

Carbon dioxide is the most important anthropogenic greenhouse gas. The global atmospheric concentration of carbon dioxide has increased from a pre-industrial value of about 280 ppm to 379 ppm in 2005. The atmospheric concentration of carbon dioxide in 2005 exceeds by far the natural range over the last 650,000 years (180 to 300 ppm) as determined from ice cores...

The primary source of the increased atmospheric concentration of carbon dioxide since the pre-industrial period results from fossil fuel use, with land-use change providing another significant but smaller contribution...

Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level...

Most of the observed increase in global average temperatures since the mid-20th century is very likely [90% probability] due to the observed increase in anthropogenic greenhouse gas concentrations."

Nov. 2007 - Intergovernmental Panel on Climate Change (IPCC) 
"A Report of Working Group I of the Intergovernmental Panel on Climate Change: Summary for Policy Makers" (4MB)  
"Uncertainty Guidance Note for the Fourth Assessment Report" (42KB)  

Barack Obama, JD, 44th President of the United States, stated in an article titled "Barack Obama's Plan to Make America a Global Energy Leader" on his presidential campaign website (accessed Mar. 13, 2008):

"Global warming is real, is happening now and is the result of human activities. The number of Category 4 and 5 hurricanes has almost doubled in the last 30 years. Glaciers are melting faster; the polar ice caps are shrinking; trees are blooming earlier; oceans are becoming more acidic, threatening marine life; people are dying in heat waves; species are migrating, and eventually many will become extinct. Scientists predict that absent major [green house gas] emission reductions, climate change will worsen famine and drought in some of the poorest places in the world and wreak havoc across the globe."

Mar. 13, 2008 - Barack Obama, JD 

Al Gore, Jr., former Vice President of the US and Chairman of the Board at the Alliance for Climate Protection, stated the following in his Jan. 28, 2009 testimony "Statement to the Senate Foreign Relations Committee," presented at The US Senate Committee on Foreign Relations hearing "Addressing Global Climate Change: The Road to Copenhagen," available at the US Senate Committee on Foreign Relations website:

"[A]s long as we continue to depend on dirty fossil fuels like coal and oil to meet our energy needs, and dump 70 million tons of global warming pollution into the thin shell of atmosphere surrounding our planet, we move closer and closer to several dangerous tipping points which scientists have repeatedly warned – again just yesterday – will threaten to make it impossible for us to avoid irretrievable destruction of the conditions that make human civilization possible on this planet."

Jan. 28, 2009 - Al Gore, Jr. 
Al Gore Statement to the Senate Foreign Relations Committee (90KB)  

The World Wildlife Fund (WWF) stated the following on its webpage "Climate: Why It Matters," available at its website (accessed Jan. 22, 2009):

"Climate change is impossible to hide and ought to be impossible to ignore. The 10 hottest years on record have occurred since 1990. Arctic sea ice has declined to the lowest levels on record and studies suggest that two-thirds of the world's polar bear population will be gone by 2050. But more than polar bears and ice caps are at risk—climate change endangers all life on our planet...

Although there has been a great deal of variability in the Earth's climate over time, many scientists believe that the changes we are seeing cannot be accounted for by natural variability alone. Climate change is a man-made problem. Human activity, primarily the burning of fossil fuels like coal and oil - along with deforestation, agriculture, and industrial processes, are responsible for the changes. Every bit of coal, every liter of oil or gas that humans burn adds to the carbon dioxide (CO2), methane and nitrous oxide in the atmosphere. These greenhouse gases trap heat in the earth's atmosphere, and have become much more concentrated since the onset of industrialization. Such increases, coupled with the incremental increase of other greenhouse gasses, have the potential to raise global temperatures between 2 ½ and 10°F over the next century."

Jan. 22, 2009 - World Wildlife Fund (WWF) 

Steven Chu, PhD, Secretary of the US Department of Energy and Director of the Lawrence Berkeley National Laboratory at the time of the quote, and José Goldemberg, PhD, Professor at the University of São Paulo (Brazil), et al., stated the following in the Oct. 2007 report "Lighting the Way Toward a Sustainable Energy Future," published on the InterAcademy Council website:

"The environmental systems on which all life depends are being threatened locally, regionally, and at a planetary level by human actions...

Linkages between energy use and environmental quality have always been apparent, from the deforestation caused by fuelwood use even in early societies to the high levels of local air and water pollution that have commonly accompanied the early phases of industrialization...

[C]limate change is emerging as the most consequential and most difficult energy-environment linkage of all. The production and use of energy contributes more than any other human activity to the change in radiative forcing that is currently occurring in the atmosphere; in fact, fossil-fuel combustion alone currently accounts for well over half of total greenhouse gas emissions worldwide (after accounting for different gases' carbon dioxide equivalent warming potential). Since the dawn of the industrial era, carbon dioxide levels in the atmosphere have increased by about 40 percent; going forward, trends in energy production, conversion, and use—more than any other factor within human control—are likely to determine how quickly those levels continue to rise, and how far. The precise implications of the current trajectory remain unknown, but there is less and less doubt that the risks are large and more and more evidence that human-induced global warming is already underway... For most of human history, animals and biomass supplied the vast bulk of human energy needs. With the advent of the Industrial Revolution roughly two centuries ago, humans began to turn increasingly to hydrocarbons as their primary source of energy, marking a profound shift that brought with it an era of unprecedented technological, socio-economic, and cultural change."

Oct. 2007 - Steven Chu, PhD 
José Goldemberg, PhD 
Part One: "LIghting the Way Toward a Sustainable Energy Future" (5.3MB)  
Part Two: "Lighting the Way Towards a Sustainable Energy Future" (3MB)  

James Hansen, PhD, Director of the Goddard Institute for Space Studies at NASA, stated the following during a June 23, 2008 briefing to the House Select Committee on Energy Independence & Global Warming titled "Global Warming Twenty Years Later: Tipping Points Near," available at the Columbia University website:

"Warming so far, about two degrees Fahrenheit over land areas, seems almost innocuous, being less than day-to-day weather fluctuations. But more warming is already 'in the pipeline', delayed only by the great inertia of the world ocean. And climate is nearing dangerous tipping points. Elements of a 'perfect storm', a global cataclysm, are assembled...

The consequences of continued increase of greenhouse gases extend far beyond extermination of species and future sea level rise...

Phase out of coal use except where the carbon is captured and stored below ground is the primary requirement for solving global warming.

Oil is used in vehicles where it is impractical to capture the carbon. But oil is running out. To preserve our planet we must also ensure that the next mobile energy source is not obtained by squeezing oil from coal, tar shale or other fossil fuels.

Fossil fuel reservoirs are finite, which is the main reason that prices are rising. We must move beyond fossil fuels eventually. Solution of the climate problem requires that we move to carbon-free energy promptly."

June 23, 2008 - James E. Hansen, PhD 

CON (no)

S. Fred Singer, PhD, Professor Emeritus of Environmental Sciences at the University of Virginia, stated the following in his May 22, 2007 article "The Great Global Warming Swindle," published in the San Francisco Examiner:

"There is no proof that the current warming is caused by the rise of greenhouse gases from human activity. Ice core records from the past 650,000 years show that temperature increases have preceded—not resulted from—increases in CO2 by hundreds of years, suggesting that the warming of the oceans is an important source of the rise in atmospheric CO2. As the dominant greenhouse gas, water vapor is far, far more important than CO2. Dire predictions of future warming are based almost entirely on computer climate models, yet these models do not accurately understand the role or water vapor—and, in any case, water vapor is not within our control. Plus, computer models cannot account for the observed cooling of much of the past century (1940–75), nor for the observed patterns of warming—what we call the 'fingerprints.' For example, the Antarctic is cooling while models predict warming. And where the models call for the middle atmosphere to warm faster than the surface, the observations show the exact opposite.

The best evidence supporting natural causes of temperature fluctuations are the changes in cloudiness, which correspond strongly with regular variations in solar activity. The current warming is likely part of a natural cycle of climate warming and cooling that's been traced back almost a million years."

May 22, 2007 - S. Fred Singer, PhD 

Over 100 international scientists wrote the following in a group letter to UN Secretary General Ban Ki-Moon on Dec. 13, 2007 titled "Open Letter to the Secretary-General of the United Nations," available at the Science and Public Policy Institute website:

"It is not possible to stop climate change, a natural phenomenon that has affected humanity through the ages...

The United Nations Intergovernmental Panel on Climate Change (IPCC) has issued increasingly alarming conclusions about the climatic influences of human-produced carbon dioxide (CO2), a non-polluting gas that is essential to plant photosynthesis. While we understand the evidence that has led them to view CO2 emissions as harmful, the IPCC's conclusions are quite inadequate... it is not established that it is possible to significantly alter global climate through cuts in human greenhouse gas emissions...

The average rate of warming of 0.1 to 0.2 degrees Celsius per decade recorded by satellites during the late 20th century falls within known natural rates of warming and cooling over the last 10,000 years."

Dec. 13, 2007 - "Open Letter to the Secretary-General of the United Nations" (328KB)  

James Inhofe, United States Senator (R-OK), stated the following in his Sep. 25, 2006 speech "Hot & Cold Media Spin: A Challenge to Journalists Who Cover Global Warming," available at the U.S. Senate Committee on Environment & Public Works website:

"I am going to speak today about the most media-hyped environmental issue of all time, global warming...

The media have missed the big pieces of the puzzle when it comes to the Earth's temperatures and mankind's carbon dioxide (C02) emissions. It is very simplistic to feign horror and say the one degree Fahrenheit temperature increase during the 20th century means we are all doomed. First of all, the one degree Fahrenheit rise coincided with the greatest advancement of living standards, life expectancy, food production and human health in the history of our planet. So it is hard to argue that the global warming we experienced in the 20th century was somehow negative or part of a catastrophic trend.

Second, what the climate alarmists and their advocates in the media have continued to ignore is the fact that the Little Ice Age, which resulted in harsh winters which froze New York Harbor and caused untold deaths, ended about 1850. So trying to prove man-made global warming by comparing the well-known fact that today's temperatures are warmer than during the Little Ice Age is akin to comparing summer to winter to show a catastrophic temperature trend.

In addition, something that the media almost never addresses are the holes in the theory that C02 has been the driving force in global warming. Alarmists fail to adequately explain why temperatures began warming at the end of the Little Ice Age in about 1850, long before man-made CO2 emissions could have impacted the climate. Then about 1940, just as man-made CO2 emissions rose sharply, the temperatures began a decline that lasted until the 1970's, prompting the media and many scientists to fear a coming ice age.

Let me repeat, temperatures got colder after C02 emissions exploded. If C02 is the driving force of global climate change, why do so many in the media ignore the many skeptical scientists who cite these rather obvious inconvenient truths?"

Sep. 25, 2006 - James M. Inhofe 

The Nongovernmental International Panel on Climate Change (NIPCC), a group of scientists led by Heartland Institute member Dr. S. Fred Singer, stated the following in its Mar. 2008 report "Nature, Not Human Activity, Rules the Climate," published on the Heartland Institute website:

"[T]he human greenhouse gas contribution to current warming is insignificant...

If current warming is not due to increasing greenhouse gases, what are the natural causes that might be responsible for both warming and cooling episodes – as so amply demonstrated in the historic, pre-industrial climate record? Empirical evidence suggests very strongly that the main cause of warming and cooling on a decadal scale derives from solar activity via its modulation of cosmic rays that in turn affect atmospheric cloudiness. According to published research, cosmic-ray variations are also responsible for major climate changes observed in the paleo-record going back 500 million years...

In conclusion, this NIPCC report falsifies the principal IPCC [Intergovernmental Panel on Climate Change] conclusion that the reported warming (since 1979) is very likely caused by the human emission of greenhouse gases. In other words, increasing carbon dioxide is not responsible for current warming. Policies adopted and called for in the name of 'fighting global warming' are unnecessary."

Mar. 2008 - Nongovernmental International Panel on Climate Change (NIPCC) 

Nathan Paldor, PhD, Professor of Dynamical Meteorology and Physical Oceanography at the Hebrew University of Jerusalem, stated the following in a Dec. 4, 2007 testimony before the US Senate Committee on Environment and Public Works:

"First, temperature changes, as well as rates of temperature changes (both increase and decrease) of magnitudes similar to that reported by IPCC to have occurred since the Industrial revolution (about 0.8C in 150 years or even 0.4C in the last 35 years) have occurred in Earth's climatic history. There's nothing special about the recent rise!

Second, our ability to make realizable (or even sensible) future forecasts are greatly exaggerated relied upon by the IPCC. This is true both for the numerical modeling efforts (the same models that yield abysmal 3-day forecasts are greatly simplified and run for 100 years!).

Third, the rise in atmospheric CO2 is much smaller (by about 50%) than that expected from the anthropogenic activity (burning of fossil fuels such as oil, coal and natural gas), which implies that the missing amount of CO2 is (most probably) absorbed by the ocean. The oceanic response to increasing CO2 concentration in the atmosphere might be much slower than that of the atmosphere (and is presently very poorly understood). It is quite possible that after an 'adjustment time' the ocean (which contains far more CO2 than the atmosphere) will simply increase its biological activity and absorb the CO2 from the atmosphere (i.e. the atmospheric CO2 concentration will decrease)."

Dec. 4, 2007 - Nathan Paldor, PhD 

Willie Soon, PhD, Physicist at the Harvard-Smithsonian Center for Astrophysics, stated the following in his Nov. 2007 article "Implications of the Secondary Role of Carbon Dioxide and Methane Forcing in Climate Change: Past, Present, and Future," published in Physical Geography:

"There is no quantitative evidence that varying levels of minor greenhouse gases like CO2 and CH4 have accounted for even as much as half of the reconstructed glacial-interglacial temperature changes or, more importantly, for the large variations in global ice volume on both land and sea over the past 650kyr [650,000 years]. This paper shows that changes in solar insolation [amount of solar energy hitting the earth] at climatically sensitive latitudes and zones exceed the global radiative forcings [greenhouse gas accumulation in the atmosphere trapping solar heat] of CO2 and CH4 by severalfold...

[T]he popular notion of CO2 and CH4 radiative forcing as the predominant amplifier of glacial-interglacial phase transitions cannot be confirmed...

Our basic hypothesis is that long-term climate change is driven by insolation changes, from both orbital variations and intrinsic solar magnetic luminosity variations. This implies natural warming and cooling variations."

Nov. 2007 - Willie Soon, PhD 

Bob Barr, JD, former US House Representative (R-GA) and 2008 Presidential Candidate for the Libertarian Party, stated the following in a May 22, 2008 interview "Glenn Talks With Bob Barr," available on The Glenn Beck Program website:

"Mankind has done a lot of good in the world. They have done a lot of bad as well, but change in the climate is not one of them. I've seen no legitimate scientific evidence that indicates that the cyclical -- and they are very much cyclical -- you know, increases and drops in global temperatures over the decades and over the centuries is the result of, you know, mankind."

May 22, 2008 - Bob Barr, JD