By Dr. Matthew Wasson, Ph.D.
The debate is over — at least in the scientific community. Over ninety-four percent of experts in the field agree that the climate is warming due to human activity. In 1998, nearly 75% of Americans believed that “solid evidence” of climate change existed. Due to a well-funded campaign by the fossil-fuel industry to create “controversy,” that number has dropped to a low of 58%.
With help from the website SkepticalScience.com, we identified the top 10 arguments used to deny human-caused effects on climate change and provide a brief summary of why those arguments are wrong or misleading.
The evidence that the Earth is warming has become overwhelming over the last few decades and many skeptics of human-induced climate change have come to acknowledge the trend, though not always the method. In the 1960s, scientific studies showed that brightness and warmth of the sun were increasing, as were the frequency of sunspots — a theory that was paired with the gradual increase in global temperatures that had occurred since the beginning of the century. Climatologists of that era erroneously believed that energy from the sun was a significant factor driving changes to global temperatures.
Since 1975, however, solar activity has been on a declining trend, while global temperatures have risen dramatically, and volumes of research has proven that solar activity cannot explain the global warming we see today.
One thing that climate scientists and global warming skeptics often agree on is that weather patterns have changed naturally in the past. However, arguing that humans cannot be responsible for present-day climate change is akin to saying humans cannot cause forest fires because natural factors have caused forest fires in the past. Almost all climate scientists agree that the current trends of rapid warming is caused by human-generated greenhouse gas and cannot be explained away by pointing to natural factors that may have caused climate variations in the past.
A recent survey of climate scientists revealed that more than 97% of active researchers believe that the earth is warming and that human activity is primarily responsible. The most respected scientific societies, such as the American Association for the Advancement of Science, the American Astronomical Society, the American Geophysical Union, the American Institute of Physics and the American Meteorological Society, all agree that global warming is happening and that it is caused primarily by human activities.
A common tactic of climate change deniers is to claim that recent cold weather events provide evidence that the earth is not warming and may actually be cooling. What the deniers may not grasp, however, is the distinct difference between long-term climate patterns, which are measured over decades, and unpredictable short-term weather events caused by factors unrelated to climate change. From average global air and water temperatures to snow cover and ice melt in polar regions, all ten of the most important indicators of climate change point to real evidence that the globe is warming.
Climate models mathematically represent a complicated set of interactions between the sun, oceans, land and atmosphere in order to predict how the overall climate will be affected by changes in any one of these systems. The models are first tested to see how well they represent historic changes in climate; if successful, they can then be used to predict how factors such as increases in greenhouse gas emissions will impact climate in the future. A number of climate models running for decades have proven to be quite accurate in their predictions, with an exception — they have significantly underestimated the amount of warming and sea level rise that actually occurred in recent decades. No one has yet developed a model that can explain recent global warming trends — without adding greenhouse gases as a contributing factor.
Global warming deniers have recently seized on studies that claim many weather stations are “improperly” located, in an effort to attribute warming over the past few decades as poorly located thermometers. It is true that increasing temperatures at some weather stations can be explained by what is called the “urban heat island effect,” where temperatures in urban areas increase as natural vegetation is replaced with pavement and asphalt. Overall warming trends, however, have been the same in both urban and rural areas and have been measured by satellites, as well as thermometers, so improper placement of weather stations cannot explain the increase in temperature seen over the past century.
It’s true that temperatures were particularly high in 1998. The six years that followed — while still some of the hottest years on record — exhibited a slightly lower average temperature than the record set in 1998. But global warming deniers seized on this short-term variability, cherry-picking individual numbers and ignoring other indicators of global warming — such as unabated increases in ocean temperatures and the melting of arctic sea ice — to argue that the earth had actually been cooling since 1998. In actuality, both 2005 and 2010 were the two hottest years ever recorded, and average yearly temperatures continued a steady climb throughout the second half of the decade.
While some scientists did propose in the 1970s that another ice age could be imminent, a survey of papers addressing the question of future climate patterns published in climate science journals between 1960 and 1979 show that 60% actually predicted a warming climate, while only 10% predicted cooling. The reports that predicted another ice age received significantly more attention in the media than the consensus that occurred by 1980 admitting that those predictions were misplaced.
The argument that Antarctica is gaining ice relies on selective use and interpretation of data. While “sea ice” (i.e. ice that occurs on top of the ocean) has increased in recent years, what is far more concerning to scientists is that “land ice” — which represents the vast majority of ice in Antarctica — is declining. As for the other pole, climate change deniers cannot debate the fact that both sea and land ice is declining in the Arctic. Overall, the rate at which ice in both polar regions is melting is consistent with some of the most dramatic predictions of climate models.
While there is no question that levels of carbon dioxide in the atmosphere have been higher in the past — such as during the Cretacious era 65 million years ago when dinosaurs walked the earth — it is also true that sea levels were hundreds of feet higher at that time and conditions would have been far less hospitable to human life than today’s climate. The predicted impacts of global warming — including sea level rise, acidification of oceans, spread of disease and reduced availability of fresh water — are far more negative than positive in most regions of the country and the world. The projected economic impacts in Appalachia and the Southeast are extremely worrisome (see story on page 18).