Human Impact on the Climate

Let me admit that writing this posting is cathartic. I’m tired of reading and hearing inanity from climate change skeptics and deniers.

On February 25, 2019 the British peer-reviewed journal Nature Climate Change published “Celebrating the anniversary of three key events in climate change science.”

Its content was picked up by numerous news outlets. The authors (Benjamin D. Santer, Celine J.W. Bonfils, Qiang Fu, John C. Fyfe, Gabriele C. Hegerl, Carl Mears, Jeffrey F. Painter, Stephen Po-Chedley, Frank J. Wentz, Mark D. Zelinka, and Cheng-Zhi Zou) reported on research and 40 years of satellite monitoring data that enabled them to draw conclusions about the human impact on the changing climate.

The Nature Climate Change article summarized the events recognizing three anniversaries, which taken together, helped identify homo sapiens (i.e., us) as affecting “the thermal structure of the atmosphere.” It described the work of various researchers and scientists who, since the late 1970’s, have been investigating whether human activity is the cause of global warming. Clearly, then, research about the changing climate is not a recent phenomena as it dates back to the 1970’s. Let’s look a bit more closely at each, as described in the article:

  • In 1979, the NAS (i.e., National Academy of Sciences) released the findings of the “Ad Hoc Study Group on Carbon Dioxide and Climate.” The NAS findings became known as the Charney Report. It is a seminal work in confirming the anthropogenic (i.e., originating from human causes) influence on climate change. The Nature Climate Change article points out that the authors of the Charney Report didn’t have access to the subsequent data and analyses that ultimately corroborated (and expanded on) much of their work, such as “thousands of relevant peer reviewed scientific papers, four decades of satellite measurements of global climate change, land and ocean surface temperature datasets measuring 120 years, estimates of natural climate variability, and sophisticated models.” In other words, their report was done without the sophisticated analyses, modeling, reporting and analytical techniques available to subsequent researchers. In spite of that, the Charney Report indicated that “We estimate the most probable global warming for a doubling of carbon dioxide to be near three degrees Centigrade with a probability error of +/- 1.5 degrees Centigrade.” In 1979. They understood that there was a link between the burning of fossil fuels and the potential rise in temperatures. They also understood how the oceans could delay any warning signals about the changing climate by absorbing heat. The authors of the Nature Climate Change article highlighted that the Charney Report authors concluded that “humanity may not be given a warning until the carbon dioxide loading is such that an appreciable climate change is inevitable.” Prescient.
  • Hasselmann’s Optical Detection Paper, also released in 1979. His paper was “On the signal-to-noise problem in atmospheric response studies.” I admit that I don’t have the background to describe the technical aspects of this work. So, I will not. As I understand it, though, prior to Hasselmann, scientists evaluated the significance of atmospheric change by measuring it at thousands of local sample sites. Hasselmann felt that it was critical to statistically measure climate change patterns globally. In other words, focus on the forest, not the trees. He also pointed out that “theory, observations and models” provide information about signal and noise properties of various features in the atmosphere. As such, their changes could be measured over time. What does this mean? Every molecular structure (i.e., carbon dioxide, methane, volcanic ash, pollutants from industrial waste, water vapor, etc.) provides a unique “signal” that can be captured and measured. The “noise” is the change in response to the signal. For example, we can measure changes in greenhouse gases (carbon dioxide, methane, etc.) in the atmosphere (i.e, the signal) and measure the concomitant rise in global temperatures (i.e., the noise.) However, it wasn’t until satellite monitoring activity began in earnest that the data was collected enabling his hypotheses to be observed and measured. Hasselmann’s work was essential for the subsequent studies that confirmed the human activity as a cause of climate change.
  • Forty years of satellite data. In 1978, NOAA (i.e., National Oceanic and Atmospheric Administration) satellites began monitoring emissions from oxygen molecules in the atmosphere. The NOAA is an agency within the US Department of Commerce. Its mission statement includes the role “to understand and predict changes in climate, weather, oceans and coasts.” During the time that NOAA satellites have been monitoring the microwave emissions it has given scientists the ability to analyze trends and variations in Earth’s atmosphere.

I also reviewed an April, 2014 article from Climate Risk Management, “A probabilistic analysis of human influence on recent record global mean temperature changes.” The authors were Australian researchers Philip Kokic, Steven Crimp, and Mark Howden. They took a different statistical approach from those noted above. Their results concluded that there was a 99.9999 percent likelihood that “304 consecutive months of anomalously warm global temperatures to June, 2010 is directly attributable to the accumulation of greenhouse gases in the atmosphere.” They performed over 100,000 simulations in their analyses. The purpose of these analyses was to support techniques to mitigate corporate risk associated with climate change. They were writing primarily for corporate risk managers who are chartered with, among other things, putting programs in place that protect the assets of their corporations. As such, they stated in their report that one of the problems of addressing solutions to the changing climate is the “degree of uncertainty as to whether observed climate changes are due to human activity or are part of natural systems fluctuations remains a major stumbling block…” Following their analysis, they believed that the results of their analyses alleviated the uncertainty.

So, from all of the above, why should we take at face value these assertions that there is a 99.9999 percent probability that human activity is the cause of global warming?

As stated in the Nature Climate Change article: “An anthropogenic fingerprint of tropospheric warming is identifiable with high statistical confidence in all current available satellite datasets.” These datasets were measured over the 40 year period by three research groups. This particular point cannot be overstated. The measurements were conducted by three independent research organizations. Two (Remote Sensing Systems and the Center for Satellite Applications and Research) of the three datasets first exceeded the five sigma threshold in 2006. Five sigma is a measure of the degree of confidence that scientists have in a result. If results exceed five sigma it means that one can be 99.9999 percent confident in them. The last of the datasets (from the University of Alabama Huntsville) exceeded it for the first time in 2016. That means that all three research organizations unanimously concluded that there is a 99.9999 percent probability that human activity is responsible for climate change. The Nature Climate Change article concludes with these prophetic words and somber warning: “Humanity cannot afford to ignore such clear signals.”

Now, let’s be crystal clear about this. We are not relying on one report concluding that there is a 99.999 percent probability of anthropogenic caused climate change. We are relying on the three independent datasets measured over the 40 year period between 1978 and 2018 and the Australian risk management analysis that came to the same conclusion using a different methodology. Four independent research groups crunched the numbers and came to that conclusion independently. Human activity is 99.9999 percent likely to be the cause of our changing climate. Case closed. It is time for action.

We must reduce the amount of carbon dioxide (and other greenhouse gases) in the atmosphere, reduce their rate of growth, and transition to sources of energy that do not contribute to the problem. We no longer have the time to waste entertaining inane concerns about the link between man and climate or accepting ongoing obfuscation by denialists. The numbers are clear.

Voters must take political and economic action by choosing the politicians that best represent their best interests and punish the economic entities acting against them. In a shot across the bow of the oil companies, the Guardian reported on March 8, that the world’s largest sovereign wealth fund, the $1 trillion Norwegian Government Pension Fund Global, indicated that it will divest itself of fossil fuel companies, with the caveat that they will retain investments of those with renewable energy subsidiaries. Even with that caveat, this is a positive step. Unfortunately, it also reflects the strength of the industry such that they were able to secure that caveat. The battle is between incontrovertible facts and the naked power of big money. Now is the time for the greater good to become paramount. If you haven’t registered to vote, there is no time like the present. If you have registered, consider your best interests when in the voting booth. We don’t have a Plan(et) B.

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