All major analyses of annual average temperatures in the northern hemisphere observe that temperatures were relatively constant from 1945 to 1969, rose one degree Fahrenheit from 1969 to 1998, remained nearly constant from 1998 through 2013 and rose 0.6 degrees from 2013 through 2016, six times faster than from 1969 to 1998.

Are humans to blame? What can we do about it? What should we do about it?

Most scientists are convinced that greenhouse gases are the culprit, yet they have never shown by experiment that greenhouse gases absorbing infrared radiation from Earth can actually cause such warming. This is odd.

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As Steven Chu, Nobel laureate and former Secretary of Energy, put it, “the final arbitrator of any point of view are experiments that seek the unbiased truth.”

How could carbon dioxide have become so important scientifically, economically, and politically without greenhouse-warming theory ever having been verified by experiment, a cornerstone of the scientific method?

I have now completed experiments showing that air with more than 23-times normal concentrations of carbon dioxide is heated no more than 0.2 degrees more than normal air when exposed to the same infrared radiation. Air with more than 10-times normal concentrations of carbon dioxide covered Earth 400 million years ago when ice ages were common.

Atmospheric concentrations of carbon dioxide have been rising steadily since 1945 at ever increasing rates. These rates do not change suddenly in 1969, 1998 and 2014 when rates of global warming changed.

Throughout the past 800,000 years, increases in concentrations of carbon dioxide do correlate with increases in ocean temperatures, but concentrations typically increase a few hundred years after observed warming. Oceans are well-known to lose carbon dioxide into the atmosphere as they warm, much like your warming beer loses its fizz.

Cores drilled through Greenland ice show that the greatest warming observed in the past 130,000 years occurred from 12,000 to 9500 years ago, when sea level rose more than 400 feet. This was the time when 12 of the 13 best-dated, basaltic, volcanic centers in Iceland were active, the highest rates of volcanism recorded in all of Greenland ice.

Throughout written history, eruptions of large amounts of basaltic lava were contemporaneous with the onset of rapid global warming, including the Medieval warm period and the Roman warm period. Ice cores in Greenland document that 25 times in the past 130,000 years, the world warmed at least halfway out of ice-age conditions within a few years when basaltic volcanoes were erupting, followed by slow cooling over centuries to millennia.

These irregular sequences averaged every 4000 years, but they were highly erratic. They were not cyclic. These footprints of climate change cannot be explained by greenhouse gases or by any of the numerous theories claiming that cyclical processes cause climate change.

Despite such clear and widely reported data, the number one “key finding” of the recent Climate Science Special Report by the U.S. Global Change Research Program concluded with “very high confidence” that “global climate continues to change rapidly compared to the pace of the natural variations in climate that have occurred throughout Earth’s history.”

This “key finding” is clearly mistaken.

The greatest known global warming and mass extinctions occurred 251 million years ago when basaltic lava covered an area of Siberia equivalent to 87 percent of the contiguous United States. Throughout Earth’s history, periods of rapid warming occurred when basalt flowed out over large areas.

The largest, most rapidly formed basalt flow since 1783 erupted in Iceland from August 2014 to February 2015, most likely leading to the observed very rapid global warming since 2014. This is why 2016 is the hottest year on record and 2017 may even be warmer.

On the other hand, global cooling appears to be caused by large explosive volcanoes that eject water vapor and sulfur dioxide into the lower stratosphere forming a sulfuric acid aerosol or mist that reflects and scatters sunlight, cooling Earth 0.9 degrees for two to four years, but lowering ocean temperatures for nearly a century.

When many large explosive eruptions occur each century and such activity continues for tens of thousands of years, observations and modeling show they increment the world cooler and cooler down into ice ages.

Chlorine and bromine gases erupted by volcanoes are observed to deplete the ozone layer, allowing more ultraviolet-B radiation from the sun to reach Earth. Ultraviolet-B is the highest frequency, “hottest” solar radiation reaching Earth where it causes sunburn, skin cancer, cataracts and much greater warming than the much “cooler” infrared radiation absorbed by greenhouse gases.

In the 1960s, chlorofluorocarbon gases (CFCs) became very popular for use as spray-can propellants, refrigerants and solvents. In 1985, with discovery of the Antarctic ozone hole, scientists realized the need to limit CFCs that transport chlorine atoms to the ozone layer where one atom of chlorine can destroy more than 100,000 molecules of ozone.

The United Nations Montreal Protocol on Substances that Deplete the Ozone Layer became effective in January 1989, mandating cutbacks in production of CFCs. By 1993 the increase in CFCs stopped. By 1995, the increase in ozone depletion stopped. By 1998, the increase in temperature stopped.

Humans had caused the warming beginning around 1969 and accidentally stopped this warming by 1998. Without the Montreal Protocol, temperatures today would likely be one degree hotter.

The problem is that ozone remains depleted, glaciers continue to melt, sea level continues to rise and the ocean continues to absorb major amounts of ultraviolet-B radiation from the sun. Ozone depletion is made worse by a substantial black market in CFCs. Plus, we are learning that ozone depletion can be caused by shorter-lived gases such as dichloromethane not regulated under the Montreal Protocol.

Ozone depletion caused by humans and by volcanic eruptions explains most periods of very rapid warming during human history and throughout Earth history in considerable detail.

Greenhouse-warming theory cannot.

If ozone depletion is the primary cause of global warming, the major increases in temperature by 2050 predicted by greenhouse-warming theory will not occur. Spending trillions of dollars to decrease emissions of greenhouse gases is likely to be a complete waste of money. We can continue to burn fossil fuels without damaging the climate, provided we minimize pollution that is killing five million people each year, especially in Asia.

Scientists, political leaders, business leaders and voters all need to come together to minimize ozone depletion and spur recovery to ozone levels widespread before 1969.

We can prosper and grow without overheating Earth.

Peter L. Ward worked 27 years with the United States Geological Survey. He was the chairman of the White House Working Group on Natural Disaster Information Systems during the Clinton administration. He’s published more than 50 scientific papers. He retired in 1998 but continues working to resolve several enigmatic observations related to climate change. His work is described in detail at WhyClimateChanges.com and in his book What Really Causes Global Warming? Greenhouse gases or ozone depletion? Follow him on Twitter at @yclimatechanges.

The views expressed by contributors are their own and are not the views of The Hill.