Responses to Common Talking Points
Frequently Raised Against Climate Science
Climate Always Changes?
Perhaps the most common talking point against climate science these days, "the climate always changes," is but a slogan designed to keep people from thinking about why climate changes.
Greenhouse gases have always been involved.
This graph shows that global temperatures have marched in lock step with the two most important, noncondensing greenhouse gases the entire 800,000-year length of the ice core record.
Greenhouse gases lag temperature changes?
About half the time, the above response will evoke a follow-up talking point, that if you look very closely, the peaks and valleys in the graph are ever-so-slightly offset. Temperatures start to move, and then greenhouse gases follow.
That much is true, but let's dig deeper so we don't miss the underlying physics.
Here's what causes us to come out of those ice ages. Earth's orbit changes, warming the poles at the expense of the equator. As the poles warm, they lose ice and become darker, absorbing more sunlight. The reflectivity of the equator doesn't change, so on balance, the earth warms. Warming oceans hold less dissolved gas, so they give off carbon dioxide and methane, which being greenhouse gases, warm the earth more, resulting in warmer oceans giving off more greenhouse gas, warming the earth still more, and the cycle continues.
That's why, when ice ages end, the vast majority of the warming follows the uptick in carbon dioxide. Greenhouse gases have always trapped heat.
- Note: natural warming occurs when oceans GIVE OFF carbon dioxide.
- In modern warming, oceans are GAINING carbon dioxide.
This is further evidence that what we're seeing is not natural.
It's the sun?
Certainly the sun has a strong influence over Earth's climate, but it can only have a a strong influence over our climate change if the sun's energy output is changing.
This graph, by NASA, shows that the sun has been very slightly cooling for the past 60 years (yellow line) even while global warming is at its fastest.
A cooling sun cannot cause global warming.
Volcanoes emit more carbon dioxide than humans do?
According to the USGS, "All studies to date of global volcanic carbon dioxide emissions indicate that present-day subaerial and submarine volcanoes release less than a percent of the carbon dioxide released currently by human activities." (Emphasis in original)
Further, volcanic activity is not significantly changed over the past 500 years, and volcanoes cool the earth slightly.
There is no scientific consensus?
There is no scientific study that concludes anything less than a 90% agreement among climate science experts that the world is warming primarily due to human activity.
On the other hand, many scientific studies concluded there is indeed a high level of scientific consensus: the world is warming primarily due to human activity.
It has been cooling for XX years now?
This talking point is a simple game of playing local or short-term variation (climate noise) against long-term trend (global warming).
Remember that climate is defined as weather averaged over a period of at least 20 years. Nearly every 20-year period of the past century has been warmer than the previous one. That makes for a very clear, long-term trend.
Computer models are unreliable?
Let's compare projections from computer models with subsequent observations. One of the earliest, by NASA's James Hansen in 1981, projected 0.6 degrees C warming between then and 2019, and that's just what has been observed.
This graph shows a thorough comparison of many computer models (gray zone) with later observations (colored lines). Source
It's good for plants?
Carbon dioxide does indeed make plants grow faster in greenhouses, where they are not limited by nutrient availability. (Even so, crops grown in high-CO2 environments are less nutritious than normal.)
However, outdoors, nutrient availability often governs. Katharine Hayhoe, climatologist and lead scientist on three National Climate Assessments so far, says, "In a warmer environment with more carbon dioxide, plants do mature faster, but they build up less plant matter, so it takes more plants to get the same yield. A large enough increase in temperature, or a change in drought risk can even eliminate those few benefits. An experiment studying the relative effects of carbon dioxide on valuable crops, as compared to common weeds, shows that in a head to head match, the weeds win hands down. Warmer conditions with higher carbon dioxide levels cause weeds to grow faster - up to three times faster than crops. Not only that, but many weeds and pests are also limited by cold. But as temperatures warm, these species are on the move too... Weeds and invasives benefit more than most crops. And high temperatures and changing rainfall and drought patterns are already wreaking havoc on food supplies around the world. Since 1980, it's estimated, climate change has already cost us $5 billion a year on average in wheat and maize losses, much of that occurring in poor countries, where any change in food availability bites deep. We are currently conducting an unprecedented experiment with our planet, and it's the only one we have. Plants, animals, and entire ecosystems are made up of a multitude of intricate connections. We may be altering those connections and affecting the species themselves in ways that we don't yet fully grasp. But we do know one thing for sure: the faster climate changes, the greater the risk for all of us."
Land ice is growing in Antarctica?
Using this talking point requires a person to cherry-pick the only study ever, out of more than a dozen, to conclude Antarctic land ice mass is increasing. That study used laser altimetry over only part of Antarctica and extrapolated mass based on a snow density equation, which is notoriously variable. All other studies show Antarctica's land ice mass to be decreasing.
The more accurate method of measuring mass comes from NASA's GRACE and GRACE-FO satellites, which measure local variations in Earth's gravity over time, and are extremely well-suited to determine changes in local mass. Located about 250 miles up and separated by about 140 miles, these twin satellites measure the gap between them to a precision equal to 1/10 of the thickness of a human hair. As the lead satellite approaches a mountain range or glacier, the local gravity causes it to speed up, and the distance between the satellites grows - only to shrink again after the lead satellite passes the mass, and then shrink and grow again as the second satellite passes over the same area. Over time, changes in local variations in Earth's gravity field show movement of groundwater and changes in glaciers. These results are far more precise than an intermittent laser altimetry study could be.
Antarctic land ice mass is not only decreasing, but that decrease is accelerating.
Sea ice is growing around Antarctica?
The trend in sea ice extent surrounding Antarctica is actually unclear. It had been slightly increasing until 2014, but it dramatically decreased in 2016. Since then it has rebounded toward its long-term average, but scientists are uncertain what this means for the long-term trend.
Obviously, the lack of a clear trend in one physical system does not overturn our understanding that the world is warming. That understanding is supported by a wealth of data from thermometers, satellites, land ice, movement of crops and habitats, time of budding and flowering, and even the clear downward trend in overall global sea ice.
Ice is growing in Greenland?
This talking point requires a smoke-and-mirrors definition game to deceive the unwary.
Greenland's "Surface Mass Balance" is indeed positive. That means it's snowing more than the surface is melting. But this does not correlate to overall mass, because "Surface Mass Balance" excludes calving where glaciers meet the ocean.
When all is taken into account, Greenland is clearly losing ice mass.
Humans emit only 3% of natural carbon dioxide emissions?
As with many talking points of those dismissive of climate science, this one starts with a kernel of truth but quickly obscures it by withholding key information. Biological activity each year really does put around 30 times as much carbon dioxide into the air as people do. But just what is that biological activity? Decay. During autumn and winter, vegetation dies and decays, releasing a lot of carbon into the air.
What this talking point omits is the fact that spring and summer exist, during which time biological activity again removes carbon dioxide from the air. So on a NET basis, biological activity maintains a stable atmosphere. Decade by decade, biological activity is responsible for ZERO increase in CO2 levels.
Meanwhile, decade by decade, human activity is responsible for ALL the increasing CO2.
You can see both these effects in this graph, called the Keeling Curve, which shows both the natural, seasonal variation and the human-caused, long-term increase.
Scientists just got done predicting an ice age?
Although many blogs and bloviators claim the scientists of the 1960s and 1970s predicted a coming ice age, that distorts the truth.
At that time, it was well-known that greenhouse gases warm the earth by trapping Earth's outgoing heat, and that aerosols cool the earth by blocking sunlight. There were a few scientists who thought the latter effect would be more significant, but the vast majority of scientific papers concluded carbon dioxide would prevail over aerosols, resulting in global warming.
Yes, even in the 1960s and 1970s, there was an 86% consensus that the world would warm due to human activity. This is confirmed via a review of the scientific literature of the time and via a summary by Exxon's chief scientist of the state of the science in 1977: "In the first place, there is general scientific agreement that the most likely manner in which mankind is influencing the global climate is through carbon dioxide release from the burning of fossil fuels."
Maybe the earth's axis is wandering?
According to NASA, "Earth’s spin axis drifts slowly around the poles; the farthest away it has wobbled since observations began is 37 feet."
Yes, Earth has a wobble - its tilt has varied up to 37 feet. That represents 0.00005 degree variation. Want to visualize that? It's like trying to see the diameter of a human hair a football field away.
That is incredibly insignificant to climate.
Water vapor is the most significant greenhouse gas?
This talking point, like many others, starts with a "true fact," but by omitting other facts, it misleads the hearers.
It's true that water vapor traps more infrared heat/light than carbon dioxide does. And it's true that, as the upper graph shows, the total amount of water vapor in the atmosphere is increasing. That forces us to ask the crucial question, did that rise in water vapor initiate modern warming, or did warming initiate a rise in water vapor? It's the classic question: which came first, the chicken or the egg?
The lower graph answers that question by displaying relative humidity. Merriam-Webster defines relative humidity as "the ratio of the amount of water vapor actually present in the air to the greatest amount possible at the same temperature." Therefore, if water vapor is causing modern warming, water vapor must increase before temperature does, so relative humidity would have to increase. Yet we see relative humidity is decreasing. This shows us that the warming is occurring first, and the additional warmth causes increased evaporation. Then, that increased evaporation increases the overall amount of water vapor in the air, which traps still more heat.
Scientists make a clear distinction between water vapor and what they refer to as noncondensing greenhouse gases, such as carbon dioxide, methane, nitrous oxide, and others. From Lacis et al 2010: "Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere. This is because CO2, like ozone, N2O, CH4, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state."
It's all just political?
In the debate about climate science, it's helpful to note that the debate is not between one political party and another. The debate is between lobbyists well funded by the fossil fuel industry and a nearly-unanimous scientific community.
Nowhere is this more clear than in ExxonMobile's own papers. By a 5:1 margin, Exxon's scientific papers agree: the world is warming because of human emissions of greenhouse gases. On the other hand, by a 7:1 margin, Exxon's advertising and editorial papers deny that. The debate really is lobbyists arguing against scientists.
The world's climate really is in crisis because of human emissions of greenhouse gases, and no amount of messaging, lobbying, and punditry can change that fact. The only thing that will change it is for society to dramatically reduce its greenhouse gas emissions.