Do scientists know that the higher concentration of carbon dioxide in the atmosphere is actually from human sources?
Yes. This is a very important question. Fine, there is clear evidence of the rise in CO2 concentrations and an unprecedented rise in the average surface, air, and ocean temperature but you also have to provide evidence that it is from human activity.
Watch the video below to see a short explanation in the three measures scientists use to verify that the CO2 concentrations come from human sources.
From the scientific journal Nature Climate Change: “An anthropogenic fingerprint of tropospheric warming is identifiable with high statistical confidence in all currently available satellite datasets” Link to the full article or a summary from Reuters
The figure (from this research) illustrates the trend in statistical confidence of three different models using data to test for indications of the human-cause of climate change. Each colored line represents a different, independent research group (see the full article for more details). As a line goes up, the level of confidence in the outcomes indicating human causation goes up.
Two important thresholds of confidence are indicated with horizontal grey and black lines. The grey line represents the 3-sigma threshold which is another way of indicating a 99.7% probability that the findings are NOT just by chance or statistical anomaly. This was surpassed by all three models in 2002. The black line represents the 5-sigma threshold that represents a 99.99994% probability that the findings are not by chance or statistical anomaly. In other words, at the 5-sigma level, if humans have not been the primary cause of global warming, researchers would only get statistical results indicating that they were 1 in every 3.5 million tests. All three models from the research groups passed the 5-sigma threshold by 2016. As scientists collect more and more data they are increasingly confident in the results that indicate that humans are the primary cause of global warming today. As the authors of the review piece state, “An anthropogenic fingerprint of tropospheric warming is identifiable with high statistical confidence in all currently available satellite datasets.”
In sum, the data from a multitude of peer-reviewed scientific research indicates that:
- the atmosphere is warming
- it is human-caused
- the odds that this is simply a statistical anomaly (irregularity or freak occurrence) are more than 1 in a million.