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How we know that climate change is happening and that humans are causing it

1. CLAIM: The facts are these: The climate of our planet is changing at a pace unlike anything seen in the natural fluctuations traced across geological records, and scientists have therefore traced this global warming trend to human activity. RESPONSE: In related posts on this site it is shown that “natural fluctuations” in the Eemian interglacial, that immediately precedes our Holocene interglacial, are greater than what is seen in our current interglacial [EEMIAN LINK] .
2. CLAIM: “The upper atmosphere is cooling while the lower atmosphere is warming,” he says. “You don’t get that without changing the composition of the atmosphere. We’re seeing changes you would theoretically see in a warming world”. RESPONSE: This is the so called “stratospheric cooling” argument. Climate models predict that the GHG heat trapping effect of atmospheric CO2 should simultaneously warm the troposphere and cool the lower stratosphere. These trends are found in the data. However, their interpretation in terms of a proof of the GHG effect of atmospheric CO2 by way of simultaneous warming of the troposphere and cooling of the stratosphere is not possible because the required correlation is not found. The analysis is presented in a related post at this site [STRATOSPHERIC COOLING LINK] .
3. CLAIM: Data from Scripps Institution of Oceanography Mauna Loa Observatory show that atmospheric CO2 concentration has been rising since 1958 with a little over 300 parts per million by volume (ppm) to over 400 ppm in 2017. Carbon dioxide made up 81 percent of the United States’ greenhouse gas emissions in 2014. Fossil fuels and certain chemical reactions produce this odorless, colorless gas that traps heat in the atmosphere. Despite sinks that remove CO2 from the atmosphere such as soils, forests, and the ocean, industrial-era emissions have steadily raised atmospheric CO2 levels to the highest they have ever been in hundreds of millions of years. Reducing fossil fuel emissions is the number one way to reduce atmospheric CO2 levels. Energy efficiency, carbon capture, and market-based controls are among the most effective measures to curb fossil fuel emissions and to stop the rise in atmospheric carbon dioxide concentration. RESPONSE: In a related post it is shown that the carbon cycle flow accounting used to attribute rising atmospheric CO2 concentration to fossil fuel emissions contains circular reasoning because this relationship is used to infer the much larger and unmeasurable natural flows of the carbon cycle [CARBON CYCLE LINK] . It is also shown with detrended correlation analysis that atmospheric CO2 concentration is not responsive to fossil fuel emissions [RESPONSIVENESS LINK] and that therefore no empirical evidence exists to support the assumed attribution of changes in atmospheric CO2 to fossil fuel emissions; or for the climate action assumption that reductions in fossil fuel emissions will reduce the rate of increase in atmospheric CO2 concentration. It should also be noted that the claim that atmospheric CO2 concentration today is the highest it has been in hundreds of millions of years is not correct  ([LINK] [LINK] [LINK].
4. CLAIM:  The U.S. Drought Monitor shows that 12.2% of the USA is currently impacted by drought with 0.34% in extreme drought conditions. A drought is a prolonged period of dry weather that occurs when there’s an imbalance between evaporation and precipitation. It’s the real-world consequence of rising temperatures and can have devastating impacts on human health, food availability, animals, and soil. Greenhouse gas reduction will help in the long term to moderate these effects of climate change.  RESPONSE: In a related post it is shown that the Palmer Drought Severity Index for eleven states of the USA from 1908 to 2018 does not show a pattern consistent with the interpretation that these drought events are driven by anthropogenic global warming or that they can be moderated by reducing fossil fuel emissions [DROUGHT LINK] .
5. CLAIM: The current rate of change of the Global Mean Sea Level (GMSL)Measured in: mm (millimeters) anomaly is a rise of 3.4 mm/year. The rise is due to melting ice and a warming oceans. Though the global sea level is also affected by short-term climate phenomena and geographic factors, it is closely linked to temperature. Sea levels rose consistently throughout the 20th century, leaving coastal regions more vulnerable to flooding, storm surges, and salt water seeping into freshwater aquifers and affecting plant and animal habitats. These changes can and should be controlled by reducing fossil fuel emissions. RESPONSE: A paper published in 2018 by Peter Clark of Oregon State University does show a statistical relationship between the rate of sea level rise and the rate of fossil fuel emissions such that sea level rise can be attributed to fossil fuel emissions and it can be argued that emission reduction will attenuate the rate of sea level rise. However, as shown in a related post, the correlation between cumulative emissions and cumulative sea level rise used in that paper is spurious  [CLARK PAPER LINK]. When the analysis is carried out at finite time scales to overcome the statistical issue in the Clark paper, the correlation reported by Clark is not found [SEA LEVEL RISE LINK] . The data do not show that the observed rate of sea level rise can be attributed to fossil fuel emissions. Thus there is no evidence that reducing fossil fuel emissions can be used to control the rate of sea level rise.
6. CLAIM: The global mean temperature estimates show that 2016 was the hottest year ever recorded, with global average temperatures reaching 1.69°F above the 20th-century average. Temperature is a direct effect of global warming. It is also the primary driver for other climate change phenomena like droughts, typhoons, hurricanes, wildfires, and habitat change. Human health and food and water availability are also tied to temperature. It is possible and necessary to control temperature rise by reducing fossil fuel emissions. RESPONSE: Climate science holds that the progress of anthropogenic global warming (AGW) must be measured as long term temperature trends. It is not possible to relate temperature events to AGW because they do not represent a long enough time span and they do not measure the rate of warming. Specifically in this case it should be considered that 2016 was a monster El Nino year and the high temperature reported here tells us about the variability of El Nino events but it does not contain information about a long term warming trend that can be interpreted in terms of global warming and climate change. These hot year and hot month events serve only to raise the fear factor among the public with an inadequate understanding of climate science and yet they are used by climate scientists themselves. The need for such alarmism in climate science implies that the science has become corrupted with activism, Please see paragraph#15 in the related post on activism in climate science [CLIMATE ACTIVISM LINK] .
7. CLAIM: The average SST in 2016 was the warmest ever recorded, averaging 0.75°C warmer than last century’s average. Our oceans absorb heat, and the more they absorb, the warmer they get. This doesn’t just affect marine life, disrupting fish populations, fueling algal blooms, and killing coral. Higher sea surface temperatures also create more atmospheric water vapor. The less heat the oceans must absorb, the cooler they’ll be. There’s only one way to accomplish that: Reduce fossil fuel emissions.  RESPONSE:  The study of SST ( sea surface temperature) as an indicator of AGW should follow the same type of analysis as global mean temperature in terms of long term trends because temperature events do not have long term interpretations. The high SST cited here is evidence of a strong El Nino year. It has no interpretation and no implication for climate change. It serves only certain activism needs and tells us nothing about AGW. Please see paragraph#15 in this related post [CLIMATE ACTIVISM LINK]
   6. CLAIM: Data for Arctic and Antarctic Sea Ice Extent measured in sq km (square kilometers) in which there is at least 15 percent ice In January 2017 show that  Arctic sea ice extent was 13.4 million sq km—1.3 million sq kim less than the 1981-2010 mean for January. The Antarctic sea ice extent was 4.0 million sq km—0.6 million sq km less than the 1981-2010 mean for January.  The polar ice caps have existed for millions of years. Not only are they a reliable indicator of climate change, but they reflect sunlight. That high albedo (reflectivity) helps deflect solar radiation, cooling off Earth. As the ice caps shrink, they stop cooling the poles. The less ice at the poles, the faster global warming will occur. In addition, the ice caps interact with animals (they’re habitat for everything from polar bears to penguins) and influence far-away weather. And as ice caps melt, they increase sea levels around the world. These changes can and should be moderated by reducing fossil fuel emissions. RESPONSE: Sea ice data for January 2017 in isolation as compared with the 1981-2010 average contains no useful information about trends in Arctic and Antarctic sea ice. Most climate scientists study long term trends in sea ice extent from 1979 to the year of the study in the summer minimum (September for the Arctic and February for the Antarctic) and the winter maximum (March for the Arctic and September for the Antarctic). Long term trends in sea ice extent for all twelve calendar months are shown for the period 1979-2018 in related posts at this site for the Arctic and the Antarctic [ARCTIC SEA ICE LINK]   [ANTARCTIC SEA ICE LINK] . These complex trends make it clear that the data posted by Popular Science to indicate that the January sea ice extent in 2017 was about 10% less in the Arctic and 15% less in the Antarctic than the average sea ice extent in the period 1981-2010 contains no useful information that can be interpreted in terms of AGW. In addition, the statement that “as ice caps melt, they increase sea levels around the world” is mysterious as melting sea ice does not raise sea level. The work done at this site shows that there are no long term trends in Antarctic sea ice  [ANTARCTIC SEA ICE LINK]  and that Arctic sea ice trends are complex and vary greatly among calendar months. Although some declining trends were found, there was insufficient correlation to attribute those changes to fossil fuel emissions. In brief, long term trends in sea ice extent are more complex than what has been implied in the Popular Science study [LINK] .

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