Most Common Arguments of Climate Deniers

Of the 197 arguments against climate change tracked by climate scientist John Cook on skepticalscience.com, this is the one most frequently invoked. The intended inference we are to draw is that because climate has changed before, blaming the current rise in temperature on human activity is incorrect.

The earth has gone through seven glacial cycles in the last 650,000 years and most of the climate changes over that period have been attributed to small changes in the earth’s orbit. The amount of variation since the end of the Little Ice Age in the mid-19th century is far too great to be assigned to variations in the earth’s orbit. In the 21st Century, global temperatures have been warmer than at any time in more than 10,000 of the past 11,300 years. By the end of this century, the Intergovernmental Panel on Climate Change (IPCC) projects the warmest temperatures ever over the past 11 millennia.

According to the IPCC, solar activity contributes about 0.1°C to warming in an 11-year solar cycle. It is true that increased solar activity may have added to warming beginning early in the last century. However, solar irradiance alone cannot explain the overall observed temperature increase since the late 1970s. Total solar irradiance actually showed a slight decrease between 1986 and 2008 according to the IPCC.

While temperatures experienced locally and in short periods can fluctuate, overall, the Earth as a whole has been warming for most of the last century. According to the IPCC, as cited by California officials, the Earth’s surface temperatures have increased by about 1.33°F over the past 100 years. Short-term, localized temperature changes do not alter the long-term trends.

Between 90% and 100% of climate scientists agree that human activity is the cause of recent global warming. A review of published research studies found a consensus of 97% among scientists that the warming of the past century is extremely likely due to human activities. The authors noted a study that challenged that finding based on studies from “economic geologists and a self-selected group of those who reject the consensus,” commenting that “the level of consensus correlates with expertise in climate science.”

The belief in the American public that there is not a reliable consensus on climate change among scientists is due in part to ExxonMobil Corporation and other energy company efforts to mislead the general public. In a 2017 peer-reviewed paper in the journal Environmental Research Letters, Harvard researchers concluded that ExxonMobil contributed to advancing climate science — by way of its scientists’ academic publications — but promoted doubt about it in advertorials.

California officials again cite the IPCC’s finding that the mid-20th century drop in global temperatures was caused by post-World War II industrialization that increased sulfate pollution by adding microscopic bits of matter to the atmosphere that reflect the sun’s rays back into space and have a temporary cooling effect on Earth’s surface temperatures. Volcanic eruptions also emit particles into the stratosphere where they contribute to cooler temperatures for a few years. The 1980 eruption of Mt. St. Helens in Washington state and Mount Pinatubo in the Philippines in 1991 also slowed down the steady rise in global temperatures.

Climate change deniers argue that increases in carbon dioxide actually lagged behind temperature changes. That is partially true. A 2012 study found that carbon dioxide levels both lag and lead with respect to temperature increases. What happens first depends on the geography. In a cycle that does not include human activity, warming can also occur. For example, some 20,000 years ago, the Earth’s orbital cycles triggered warming in Greenland and the Arctic that melted large amounts of ice, warming the Earth’s oceans. As the southern oceans warmed, they released more carbon dioxide, causing the entire planet to warm. The correlation, however, is exactly opposite today: Human activity is pumping more carbon dioxide into the atmosphere, causing surface temperatures to rise.

The sun, as noted earlier, does have an effect on Earth’s temperatures and it has accounted for a small amount of warming. When Mount Pinatubo in the Philippines erupted in 1991, the resulting particulate matter lowered global temperatures by about 0.6°C, but the effect was temporary. While ash from volcanoes and wildfires and industrial pollution can cool the Earth by reflecting sunlight back into space, they can also settle on the snow and reduce the reflectivity (albedo) of snow cover. In the Arctic, this effect is speeding up the ice-melt.

This statement is half true. Arctic sea ice has been around for about 47 million years, but researchers have found periods when the sea-ice pack was severely reduced or even ice-free during the summer. The last such event occurred more than 11,000 years ago, and the northern high latitudes cooled until late in the 19th century when a new round of ice loss began. The suddenness and extreme magnitude of the loss is “unexplainable by any of the known natural variabilities.”

Climate models cannot predict what the temperature will be tomorrow (that is weather forecasting), but they can make accurate predictions about future large-scale warming by mapping previous climate changes. While global temperatures have naturally risen in the past, the only way to explain the rapid rise over the past 30 years is by adding in human activity. There is no other way to account for the huge jump.

This objection is a corollary to the one immediately above. Predicting next week’s weather is not the same as identifying climate trends over longer periods of time. There is virtually no doubt that Earth’s weather will be warmer in the future.

Anything’s possible, but this seems highly unlikely. There is no evidence to support this claim (and using Al Gore as an example of getting rich on climate change is ignorant). Scientists who participated in the IPCC’s climate assessments were not paid and neither are those who participate in National Academy of Sciences panels. There are better ways to get rich.

There is no evidence that this is true. Generally, research published in academic journals is vetted in a peer review process. Some research that does not meet the discipline’s standards is returned for corrections and some never meets the required standards at all.

This remains the top conspiracy theory among climate change deniers. Conspiracists got a big lift in 2009 when more than 1,100 emails and other documents were stolen from a climate research center in the United Kingdom that reportedly — and falsely — showed that data in some climate research had been manipulated to arrive at pre-set conclusions. Everyone involved in climate science was tarred with the same brush. Except, of course, none of the charges were true.

The effect of clouds on climate is still being debated. High clouds trap more heat, while low clouds reflect more sunlight back into space. The science, including ship-based observation, satellite imaging, and climate models, indicate that even though clouds have some cooling effect, it is unlikely the effect will be large enough to offset human-caused warming.

This claim may also be partially true. For example, warmer temperatures in higher latitudes could lead to higher agricultural production. But this assumes no change to the water supply in these regions and that the newly available soil will grow something. In other places, of course, crops will fail due to high temperatures and lack of water. The overall effect of the benefits of a warmer climate are not enough to offset the expected harm.

The standard answer to this claim is, “Yes, but the cost of doing nothing is even higher.” Yale economist William Nordhaus won a Nobel Prize in economics in 2018 for his work on mitigating climate change. He argues that the social cost of carbon is “the most important single economic concept in the economics of climate change.” In a study published in 2017, Nordhaus set the price of carbon at $31 per ton in the United States based on 2015 data and estimated a 3% per annum growth rate for the period to 2050. In 2015, U.S. carbon emissions totaled about 5.4 billion tons. That works out to $167 billion or about 0.9% of U.S. GDP ($18.12 trillion) in 2015. Compare that to the impact on U.S. GDP of the tax cut act passed in late 2017 that reduced U.S. revenues by 9.1% of GDP, or about $1.7 trillion, in 2018 alone.

Cutting tax revenues by $1.7 trillion does nothing to mitigate climate change while taxing consumers and businesses $167 billion could, in fact, do something.