Evidence of Climate Change from Global Warming Caused By Human Activity
Carbon Dioxide a Greenhouse Gas
Since the late 19th century chemists have know that carbon dioxide and methane absorb the heat created by sunlight, trapping a large proportion of it from escaping back into space. This is known as its greenhouse effect. In fact, without carbon dioxide in the atmosphere the earth may become to cold for most forms of life.
The evidence shows that amount of carbon dioxide in the atmosphere has been increasing since the industrial revolution of the 19th century, mainly due to human activities like the increased burning of fossil fuels, such coal and natural gas for electricity generation and refined oil products, such as gasoline, diesel and jet fuel, for transportation. You just have to look at all the cars, trucks and airplanes around us an the widespread electrification we have today that did not exist before the 1880’s. From NOAA, see Figures 1 and 2 and read: Climate Change: Atmospheric Carbon Dioxide
Figure 1
Carbon Dioxide Concentration For Last 800,000 Years
in Parts Per Million
Figure 2
Carbon Dioxide Concentration, Dec. 1975 to Jan. 2019
In Parts Per Million
The Number of Carbon Dioxide Molecules Per Million Molecules of Dry Air.
The amount of methane (and other greenhouse gases) has been increasing due mainly to expanding cattle herds, rice cultivation and leaks in natural gas pipelines. But its increase has been much less than that of carbon dioxide. From NOAA, see Figure 3 and read: Climate Change: Atmospheric Carbon Dioxide.
Figure 3
Rising Temperatures, Melting Ice Caps and Rising Sea Level
Average global temperatures have been rising since the early 20th century. From NASA, see Figure 4 and read Earth Observatory.
Figure 4
Annual Temperature Anomalies
Changes from the Base Period of 1951-1980
(The global mean surface air temperature for that 1951-1890 was estimated to be 14°C (57°F), with an uncertainty of several tenths of a degree.)
Mountain glacier and the polar caps have been melting. From NASA, see: Arctic Sea Ice, Ice Loss in Glacier National Park, Glaciers and Figures 5 and 6, taken from the Arctic area in the month of September of of 1979 and 2019. There has been no significant ice loss in Antarctica during the same period.
Figures 5 and 6
Arctic Sea Ice
Ocean levels have been rising and are starting to flood low lying coastal areas. From NASA, see Figures 7 and 8 and Sea Level.
Figure 7
Seal Level Change in Millimeters, 1870-2013
Figure 8
Sea Level Change in Centimeters, 1992-2018
Hurricanes
Ocean temperatures could be increasing the wind speeds of hurricanes, but not likely their numbers. See NOAA, Global Warming and Hurricanes. Anyone who has ever seen a weather report on a hurricane knows that hurricane activity rises and falls with the ocean temperatures. See Figure 9 below created with data from NOAA Hurricane Research Division and the website seetemperatures.org. However there is not enough evidence so far to positively prove that hurricane intensity or frequency has increased over the years with rising temperatures. See NOAA, Global Warming and Hurricanes, “detection and attribution”. Global warming is also likely increasing rainfall in some areas and reducing it in others which is disruptive to human agriculture and natural plants and animals. See Precipitation Measurement Mission, from NASA.
There are other environmental damages, like increased ocean acidity of 30% from the absorption of more CO2 by the oceans from the air. This change in ocean chemistry is adversely affecting many ocean creatures that are adapted to the lower levels of acidity existing before the industrial revolution. As with other environmental changes, when the change is too fast, some species will not have enough time to adapt through natural selection and they become extinct. See Ocean Acidification from University of California, Davis.
Figure 9
What is important about the above seven data observations is that they are consistent with each other. One would expect that, if CO2 concentrations rise, temperatures rise, and if temperatures rise, glaciers start melting, therefore, ocean levels start rising and their acidity increase. And that is what the data actually shows us.
Temperature Fluctuations from Natural Causes
Of course, there are also natural fluctuations in the earth's temperature related to CO2 and dust produced by volcanoes, cyclical changes in the earth's orbit and tilt and in the intensity of the sun's heat. However, during the period since the start of the industrial revolution in the 19th century these have played a far smaller part in affecting climate then human activities.
Volcanoes
Volcanoes release less than 2 percent of the equivalent amount of CO2 released by human activities. And they also disperse dust throughout the atmosphere that reduces sun lite for about two years, lowering temperatures. But they help melt ice sheets by depositing dark ash, which absorbs more heat from the Sun. See What do volcanoes have to do with climate change? and The year without a summer from NASA.
Changes in the Orbit and Tilt of the Earth
The earth’s orbit around the sun is elliptical, but the degree of stretch of the ellipsis varies in two separate cycles of about 100,000 and 405,000 years each. There is also a 41 thousand year cycle of the degree of tilt of the earth and a 23 thousand year cycle of its wobble as it spins. This causes temperature variations. See Earth's orbital changes have influenced climate, life forms for at least 215 million years from Columbia University and Milankovitch Cycles and Glaciation form Indiana University Bloomington. However, all these cycles take such a long period that their effect on the climate is barely noticeable during the period less most than 200 years since significant amounts of CO2 started being emitted by human activity.
The Intensity of the Sun’s Heat
From the graph below one can see that between 1880 and 1955 there was some correlation between rising solar activity and rising temperatures. But after 1955 temperatures began to rising at a faster pace and the solar activity has been declining. Therefore, we can rule out the intensity of the sun as a cause of global warming since 1955. See Is the Sun causing global warming? from NASA.
Figure 10
Implications for the Future
Believing that global warming is not a hoax, does not mean that we have to accept all of the claims about inevitable destructive effects or the results of specific forecasts of temperature increases or changes rainfall patterns. The climate is a very complex system, more complex then the economy. Having worked with statistical economic models, I have learned to be very skeptical about precise specific forecasts based on any statistical models of a complex system.
However, the one thing that I have concluded from this analysis about the future is that, if the concentration of gases with greenhouse effects in the atmosphere continues to increase at the current rate, they will cause temperatures to rise above where they will otherwise be. I do not know by how much. But one can see the correlation between increases in CO2 concentration and global temperatures, reductions in polar ice caps and rise in sea levels clearly on the graphs above. Therefore, it is very reasonable to assume that if CO2 concentrations continue to rise at the same rate, temperatures and seal level rises and other adverse effects will follow. And, without a special effort to prevent it, an increases in concentration CO2 will continue as a result of growth in population and increased economic activity.
Global warming will have some favorable disruptions, such as lengthening the crop growing seasons in cold weather areas. But it will have more unfavorable effects, such as: (1) flooding of low-lying coastal areas due to rising sea levels from melting glaciers and polar ice caps, (2) changes in rain patterns by area that creates some droughts and floods requiring considerable adaptation efforts, (3) increased ocean acidity and (4) more species becoming extinct because these changes are happening too fast for them to adapt to them through natural selection.
Despite the limitations of specific forecasts on this subject, I believe that there is enough evidence that harmful global warming caused by human activity has already happened. And even if, with luck, some natural fluctuations offset some of the warming trend, there is a high probability that global temperatures will continue to increase and cause serious damage if no action is taken to reduce them. And I believe that the probability is high enough to warrant taking action now.
The Reliability of the Evidence for Climate Change from Global Warming
My opinion on this subject, as someone who is not a climatologist, depends on the veracity of data published by the experts. (as reflected in the references and links on this page). All of us who are not experts on a particular field have to make a judgment on the reliability of published sources. My experience on the subject of source reliability leads me to these observations:
We Americans live in a country with a very free, and even aggressive, press much of which is regularly looking for wrongdoings done by government and businesses for them to report.
The data on global warming and its consequences comes from a large variety or government, private institutions and individual climatologists. It involves many people over many years and there is consistency among the sources and types of data. And they all point to global warming generated by human activity (though there is a minority that questions the quality of some of the data or arrives at a different interpretation of it). However, with so many people involved, it is practically impossible to have all of them conspiring to falsify the data that I have presented here. And that data is the reason for my opinion.
I am quite aware that governments and private companies have gotten away with lying to the public over a few years. Some of the well-known cases are: Enron's financial statements, Purdue Pharma (backed by the FDA) declaring that its opioid only has a 1% chance of addiction in long term use and Lyndon Johnson fabricating the Gulf of Tonkin incident to justify escalation of the Vietnam War. And who knows how many other cases there are that have not yet been discovered.
But to claim that the data I have quoted on this blog is fake is like the conspiracy theory that contends that the 1968 trip to the moon was staged in a TV studio. There were just too many people working at NASA that would have had to know when and where each rocket launch was scheduled to go, or worked on tracking the rockets and space capsules. And about a dozen people would have worked in the TV studio. So surely, more than one of these people would have reported any fake moon shot to the media.
I believe that those conservatives and libertarians that outright reject global warming as a hoax, are either: (1) being influence by propaganda from the fossil fuels industry or (2) having a knee-jerk reaction to the global warming claims just because they come from liberals who they, understandably, suspect of being biased in favor of any policies that involve more government spending and regulation of private businesses.