Over 97% of climate scientists agree that human activity is driving global warming, and a 2021 review of peer-reviewed literature put that figure above 99%. But a small number of scientists, a network of politically oriented think tanks, and fossil fuel industry groups have publicly challenged either the science itself or the case for action. Understanding who disagrees, and why, helps separate genuine scientific debate from organized opposition.
The Scientific Consensus Is Overwhelming
Multiple independent analyses over the past decade have measured agreement among climate researchers. A widely cited 2013 study in Environmental Research Letters reviewed nearly 12,000 peer-reviewed papers and found 97% endorsed human-caused warming. A follow-up in 2021, published in the same journal, surveyed Earth scientists with a decade more data and confirmed agreement above 99% in the peer-reviewed literature. NASA, the American Association for the Advancement of Science, and every major national science academy in the world have issued statements affirming this position.
That leaves a very thin slice of credentialed researchers on the other side. The disagreement that does exist tends to cluster not around whether temperatures are rising, but around how sensitive the climate is to carbon dioxide and how urgently societies need to act.
Scientists Who Have Publicly Dissented
The most frequently cited scientific skeptic is Richard Lindzen, an atmospheric physicist at the Massachusetts Institute of Technology. Lindzen does not deny that CO2 is a greenhouse gas. His core argument is that the climate is far less sensitive to CO2 than mainstream models project. In 2001, he proposed what he called the “iris effect,” a hypothesis that tropical cloud systems act as a thermostat, opening up to release more heat into space as the surface warms. If true, this negative feedback would significantly reduce warming projections. Most subsequent research has not supported the iris hypothesis, and Lindzen’s estimates of climate sensitivity sit well below the range accepted by the broader field.
Frederick Seitz, a former president of the U.S. National Academy of Sciences, was another prominent voice of dissent before his death in 2008. Seitz was a solid-state physicist, not a climate scientist, but his institutional prestige gave weight to petitions and open letters questioning the urgency of climate action. This pattern, where dissenters hold credentials in adjacent fields rather than climate science specifically, is common among the small group of skeptical voices.
Think Tanks and Organized Opposition
Much of the visible disagreement with climate science comes not from university labs but from conservative policy organizations. Research published in American Behavioral Scientist found that conservative think tanks play a central role in manufacturing uncertainty about climate science, often by publishing books and reports that challenge mainstream findings. The organizations most active in this space include the Competitive Enterprise Institute, the Heartland Institute, the Cato Institute, the Marshall Institute, and the Hoover Institution. The Cato Institute alone published five books questioning climate science, and the Heartland Institute published four.
These think tanks grew into their climate roles partly by filling a gap left by the Global Climate Coalition, an industry group that disbanded in the early 2000s after several major corporations broke ranks. The Cooler Heads Coalition, centered at the Competitive Enterprise Institute, emerged as its successor, coordinating messaging across organizations. Major corporate associations like the U.S. Chamber of Commerce and the American Petroleum Institute have also historically opposed policies aimed at reducing carbon emissions.
The financial picture matters here. Fossil fuel companies worried about regulation and conservative groups philosophically opposed to government intervention found common cause in attacking the scientific evidence for human-caused warming. Economic self-interest plays a documented role: corporations and industries that would bear the cost of emissions cuts have funded campaigns to keep the science looking uncertain, even as the actual uncertainty among researchers has narrowed to nearly zero.
The Main Arguments Skeptics Make
Climate disagreement isn’t one argument. It’s a ladder of positions, each conceding a bit more ground than the last. Penn State’s College of Earth and Mineral Sciences identifies several distinct tiers.
- “Warming isn’t happening.” The most extreme position holds that temperature records are unreliable. Some skeptics have pointed to discrepancies between ground-based thermometers and satellite measurements. NASA addresses this directly: ground thermometers measure temperature where people live, while satellites measure the brightness of the atmosphere at various altitudes (up to about 23,000 feet) and rely on complex modeling to convert that brightness into temperature estimates. Data from over 16 different satellites launched across different decades must be stitched together. Ground stations are considered more accurate and direct.
- “It’s natural, not human-caused.” This argument points to solar cycles as a primary driver. Solar activity did increase during the first seven decades of the 20th century. But satellite observations show the Sun’s brightness varies by only about 0.1% between solar peaks and valleys. NOAA data indicates solar changes could account for roughly 0.01°C of the 0.95 to 1.2°C warming observed since pre-industrial times. That is about 1% of the total.
- “CO2 and warming are actually beneficial.” Some skeptics argue that higher temperatures, more rainfall, longer growing seasons, and CO2 fertilization will boost agriculture and open up northern regions for farming.
- “The problem is real but the cost of action is too high.” This final position accepts the science but argues that the economic impact of deep emissions cuts would cause more harm than the warming itself. It often frames climate policy as a threat to economic growth, jobs, and energy affordability.
These arguments tend to shift over time. As temperature records become harder to dispute, more skeptics move down the ladder toward accepting warming but questioning its cause, its severity, or the wisdom of expensive interventions.
Where Climate Models Get Criticized
One area where skeptics find real scientific debate to latch onto is climate modeling. In the most recent round of international model comparisons (CMIP6, released in 2019), 10 out of 55 models projected climate sensitivity above 5°C of warming for a doubling of CO2. Previous model generations had clustered between 2°C and 4.5°C. Even climate scientists flagged these “too hot” models as a problem. A landmark study that relied on paleoclimate records and direct observations rather than model outputs placed climate sensitivity between 2.6°C and 3.9°C.
The issue was traced partly to how the models handle clouds, particularly in the tropics, where some models predicted excessive warming. The Intergovernmental Panel on Climate Change addressed this in its most recent assessment by rating models on how well they replicated historical temperatures, then weighting the more skillful models in its official projections. The result: IPCC’s assessed warming estimates came in up to 0.7°C cooler by 2100 than a simple average of all models would suggest.
Skeptics sometimes present model imperfections as evidence that climate science is fundamentally unreliable. But the corrections went in both directions (some models also underestimate certain feedbacks), and the core finding that doubling CO2 will produce substantial warming has remained stable across three decades of increasingly sophisticated modeling.
Why Disagreement Persists
The gap between 99% scientific agreement and widespread public doubt is not an accident. It reflects decades of strategic communication by industry groups and think tanks designed to make the science look more uncertain than it is. The playbook is borrowed directly from earlier campaigns by the tobacco industry to cast doubt on the link between smoking and cancer.
Political identity also plays a major role. In the United States especially, acceptance of climate science correlates strongly with political affiliation. Conservative think tanks have woven climate skepticism into a broader ideology centered on free markets and opposition to regulation, making it as much a cultural marker as a scientific position.
Economic anxiety adds another layer. Communities dependent on fossil fuel extraction, refining, or power generation face real consequences from decarbonization policies. For workers and families in those regions, skepticism can feel less like a scientific stance and more like self-preservation.