What to do if you don’t believe that man-made emissions of carbon dioxide (CO2) are causing a global warming catastrophe? Here are some ready-made responses, the next time someone questions you.

You don’t believe in global warming?

Yes, I do. The earth has warmed by roughly 0.8 degrees Celsius over the past century or so.

You don’t believe in climate change?

Yes, I do. The earth’s climate has changed several times, just in the past 1,000 years.

CO2 levels are rising and the earth is warming.

Carbon dioxide concentrations have risen from roughly 0.028% of the earth’s atmosphere in the late 1800s to the current 0.040%. However, solar output has also increased significantly in that time. If the correlation between solar variability and the climate swings of the past few thousand years is any indication, this rise in solar activity offers a valid explanation for the overall increase in temperatures seen over the past century.

Solar activity and temperature trends don’t match up in recent years.

Solar activity actually peaked somewhere around the middle of the 20th Century, and at elevated levels not seen since the Medieval Warm Period (1,000 years ago) or the Roman Warm Period (1,800 years ago.) Solar activity remained at this high level through the start of the 21st Century, with temperatures rising at the same time. While the UN’s Intergovernmental Panel on Climate Change (IPCC) claims that changes in solar “irradiance” have little impact on climate, other research argues that accompanying variations in the solar wind and solar magnetic field contribute significantly to changes in global climate. In fact, Russian scientists studying solar variability now worry that declining solar activity could lead to globally cooler temperatures by 2030.

But CO2 levels are the highest in 800,000 years.

CO2 levels in the atmosphere are currently among the lowest ever recorded in the earth’s long history. The past 800,000 years is a convenient timeframe to cite, however, since the earth has undergone repeated glacial cycles in that time—which has reduced atmospheric CO2.

CO2 is a greenhouse gas. More CO2 means more warming.

CO2 possesses a major limitation as a greenhouse gas, and one that casts doubt on its ability to function as the sole agent of climate change. As demonstrated in laboratory studies, CO2 exponentially loses heat-trapping capacity as its concentration increases. This happens because, even in minuscule quantities, CO2 quickly becomes opaque to a certain spectrum band of infrared radiation. Essentially, CO2 rapidly absorbs all of the infrared radiation it can. Adding additional quantities of CO2 to the atmosphere will not contribute much additional heat-trapping function. CO2 is also a “well-mixed gas,” which means that its concentrations are distributed throughout the atmosphere. Consequently, its heat-trapping function is essentially reaching a saturation point throughout the troposphere and stratosphere.

But higher CO2 levels mean higher temperatures. I saw that graph in “An Inconvenient Truth.”

Al Gore left out a key point when citing the parallel relationship between historical levels of atmospheric CO2 and temperature. Carbon dioxide dissolves in water, with cold water able to hold more CO2 than warm water. When the climate cools, the oceans cool—and draw in more CO2 from the atmosphere. When the climate warms, as seen at the start of the most recent interglacial period (roughly 18,000 years ago), the oceans gradually warm, releasing CO2 into the atmosphere. (A good visualization for this is a bottle of soda kept in hot sunlight. If the temperature rises high enough, the bottle will leak or burst— because the warmer soda water is no longer able to hold all of the dissolved CO2.) The point is, when global temperatures change, atmospheric CO2 inevitably follows along.

Scientists say that CO2 is warming the earth.

Yes, CO2 is a greenhouse gas, and it helps to maintain warmth in the atmosphere. But as noted above, CO2’s heat-trapping function is essentially saturated by the current level of 0.04%. Furthermore, climate models actually project that most of the presumed “man-made” warming will come from an increase in atmospheric water vapor. The principal idea of “anthropogenic global warming” (AGW) is that the small amount of additional warming contributed by CO2 (before it becomes saturated) will cause more water vapor to enter the atmosphere. Since water vapor is the primary greenhouse gas of the atmosphere (and is responsible for roughly 80% of the “greenhouse effect”), this water vapor will create “positive feedback” for further warming. Unfortunately, the AGW theory essentially disregards the cooling feedback caused by clouds (since atmospheric water vapor inevitably transitions to cloud cover.) Clouds provide net cooling by reflecting solar radiation back into space, shading ground surfaces, and producing rain (which not only cools surface temperatures but also scrubs atmospheric CO2.)

But 97% of scientists believe in global warming.

What’s most amusing is that, truthfully, no one really knows how many scientists there are in the world. Or what they all think about global warming. Or how many of them work in relevant scientific disciplines. However, the “97% consensus” is a flawed statement. Only 32.6% of the papers examined in the infamous John Cook study actually stated a position endorsing anthropogenic global warming. However, 97% of those said that “recent warming is mostly man-made.” And so what we have is a misleading statement that has become misrepresented and cited as fact. (Interestingly, there is a website called The Petition Project that lists more than 30,000 scientists who have publicly declared their disagreement with the theory of catastrophic man-made warming.)

2015 was the hottest year ever, and now 2016 is even hotter.

The warm temperatures experienced in 2015-2016 are the direct result of a strong El Nino.

El Nino is caused by global warming.

El Nino is a naturally occurring phenomenon. It happens when prevailing winds start to fade after several years of progressively “piling up” water in the western Pacific Ocean. This surplus, warm water washes back over the eastern Pacific, releasing tremendous amounts of heat. 2015’s spike in temperatures was due to El Nino. It would be dishonest and inaccurate to claim that 2015’s increase in surface temperatures was simply due to man-made warming. And even climate “alarmists” admit that El Nino is not a manifestation of man-made warming.

The “pause in global temperatures” is just people denying that the earth is getting hotter and hotter.

Satellite measurements from both UAH-Huntsville and RSS clearly show a “pause” in global temperatures (I.e. a net flatlining of temperatures) over the past 15-20 years. As the current El Nino fades, it’s reasonable to expect a resumption of recent global temperatures. More significantly, the “pause” has been the subject of numerous debates and research papers. Climate alarmists don’t deny that it has happened, and instead offer varying explanations. Even Michael Mann, creator of the infamous “Hockey Stick” graph, says that the pause occurred and was not foreseeable.

NOAA says there’s no “pause” in global warming.

There is legitimate concern as to the accuracy and reliability of recent temperature measurements being reported by the National Oceanic and Atmospheric Administration (NOAA.) Last year, NOAA reported adjustments to global temperature records that suddenly “erased” the pause. I.e. Earlier decades were revised to be “cooler,” while recent years were suddenly marked as “warmer” by factoring in measurements that included seawater temperature readings from the engine manifolds of ocean-going vessels. Various academic papers have debunked NOAA’s “new” temperature findings, but NOAA’s revised measurements continue to be used to make claims such as “warmest year ever.” The questionable methods utilized by NOAA to assemble its “pause buster” study are now the subject of a Congressional investigation.

But the oceans are becoming acidic.

The oceans remain comfortably alkaline, as they have for millions of years. As noted above, atmospheric CO2 levels have typically ranged far higher throughout the earth’s history, yet the oceans never became acidic. In fact, if they had, submarine fossil layers would have readily dissolved. Claims of the ocean “becoming acidic” are actually a misrepresentation of variations in the ocean’s pH scale. Seawater has typically measured roughly 8.18 on the pH scale. Recent, pH levels of 8.10 have been noted, which would mean slightly less alkaline oceans. But it’s misleading to say that the oceans are “becoming acidic,” particularly when ocean pH often varies greatly, based on season and location.

But the glaciers are melting.

Even NASA has stated that Antarctica’s ice cover is growing, not shrinking.

But there are more hurricanes and more tornadoes.

The U.S. has reached a record 127 months without a major hurricane. The U.S. is also at its lowest 3-year tornado total since 1950.

But we need to cut dangerous carbon pollution.

The “carbon pollution” you hear so much about is carbon dioxide, also known as CO2. It’s what all animals (including humans) breathe out, and what plants absorb. In fact, rising CO2 concentrations in the atmosphere have led to a progressive “greening” of global plant life in recent decades. Because atmospheric CO2 is at such historically low levels, the world’s plants and oceanic phytoplankton are currently rejoicing in this slightly more abundant supply of nourishment.

To conclude, it’s helpful to study the basic issues involved in the climate debate (as well as recent geologic history) when considering various aspects of global warming.