Are humans the main cause of global warming?

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Subject classification: this is a science resource.

Global warming (the major consequence of climate change) poses a very real threat to the world's ecosystems and to human life. Some doubt its existence and others say that human activity is responsible for global increases in temperature and related weather phenomena. This debate takes it for granted that global warming exists but asks to what extent humans create or hasten those conditions.

Are humans the main cause of global warming?

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  • Argument for Almost all—roughly 97%—earth scientist say that global warming is real, has been occurring throughout the 20th and 21st centuries, and has a substantial man-made component.[1][2][3]
    • Objection This is an argument from authority. Experts have been wrong many many times in the past and must prove their contentions like everybody else. Ex: 99.9% of bishops agree there is a God. This does not necessarily make it true. The global temperature has been increasing and variable for many thousand of years. The argument should be about whether change has become more rapid and how much of that is attributable to humans.
      • Objection Scientists know more about global warming than random people. Though all of us have equal rights, some people have more informed opinions and a better understanding of information than others.
      • Objection Yes, it's an argument from authority, but that doesn't change the fact that ~97% of experts agree. The argument should remain "sustained" and each reader will judge its weight.
      • Objection Likening bishops to climate scientists is highly questionable. Climate scientists do prove their assertions with their work. A bishop is obligated to uphold the belief of God's existence, if a bishop is not doing so, why are they are a bishop? A scientist's purpose is not to uphold predetermined beliefs, but to discover what is objectively true through material evidence.
        • Objection Only mathematicians "prove" their assertions. If empirical scientists proved their assertions, they wouldn't have been wrong before. Empirical scientists can only provide strong arguments for their conclusions, but they can always be wrong, as so many of them have been before. Thus citing their authority is not enough. Their actual arguments must be provided.
          • Objection Scientist´ actual arguments were provided above, in the citations [1][2][3]. There are tons of papers with concrete a strong arguments that prove that climate change is human-driven, like the IPCC reports (each consisting of about 1500 pages).
  • Argument against Science shows that climate change is happening but not that it's influenced by human activity.[citation needed]
    • Objection That is actually the opposite of what the science says: virtually all climate scientists agree that human activity is accelerating any natural process of global warming.[1][2]
      • Objection That is not entirely accurate. The science is often using abductive reasoning and is also using "post hoc, ergo propter hoc" arguments by looking at correlations and extrapolating. Much is overstated and used to back up one political narrative whereas looking at actual data suggests a more complex argument is needed. For instance roughly 60% of the greenhouse effect is caused by natural water vapor (i.e. clouds), not CO2. Methane is often also discussed. Methane is indeed 25× more potent than CO2 as a greenhouse gas, however the concentration is 1/200th that of CO2 in the atmosphere so its contribution is effectively negligible—especially as it also comes from natural sources such as the wetlands we keep preserving so not all of it can be prevented. It is true that only part of this addition gets absorbed again and hence the effect is incremental but we also need to acknowledge natural processes have a habit of correcting themselves such as high CO2 encourages more growth of carbon sinks.
        • Objection There are no quotes from a high-impact peer-reviewed article to prove this point. Without citation, this "argument" is invalid.
        • Objection "Looking at correlations and extrapolating" is a key element of science and it's not abduction but induction: one of the pillars of the scientific method.[4] If humans have such a small impact on global warming, then why would we curb our pollution? The argument that overstatements may embolden the opposition is also irrelevant if no one is overstating them: which statements are inaccurate?
  • Argument against The most extensive melting of polar ice caps occurred in 2005. The second most extensive melting of polar ice caps occurred in 2016.[citation needed] The sunspot cycle, the major one, has a period of 11.2 years. This suggests that humans are a secondary cause, not the primary one.
    • Objection All this shows is that human climate impact aligning with the sunspot cycle increases global temperatures more than solely human impact. Humans can still be the primary cause with the sunspot cycling still having an effect.
    • Objection It's true that the sunspots have an 11.2 year cycle, and that it affects Earth climate. However, data shows that since ~1960 solar irradiance has steadily declined irrespective of sunspot cycles, while Earth temperature has increased.[5]
    • Objection The melting of polar ice caps is not the only indicator of global warming. Still, polar ice caps are actually melting[6] at an alarming rate.
    • Objection I has been said that "This suggests that humans are a secondary cause, not the primary one", but no high-impact, peer-reviewed article is cited to prove it. Please provide it, otherwise it´s an opinion, not an argument.

See also

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Notes and references

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  1. 1.0 1.1 1.2 "CLIMATE CHANGE 2014: Synthesis Report. Summary for Policymakers" (PDF). IPCC. Retrieved 1 November 2015. The following terms have been used to indicate the assessed likelihood of an outcome or a result: virtually certain 99–100% probability, very likely 90–100%, likely 66–100%, about as likely as not 33–66%, unlikely 0–33%, very unlikely 0–10%, exceptionally unlikely 0–1%. Additional terms (extremely likely: 95–100%, more likely than not >50–100%, more unlikely than likely 0–<50% and extremely unlikely 0–5%) may also be used when appropriate.
  2. 2.0 2.1 2.2 "CLIMATE CHANGE 2014: Synthesis Report. Summary for Policymakers" (PDF). IPCC. Retrieved 7 March 2015. The evidence for human influence on the climate system has grown since the Fourth Assessment Report (AR4). It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together
  3. 3.0 3.1 America's Climate Choices: Panel on Advancing the Science of Climate Change; National Research Council (2010). Advancing the Science of Climate Change. Washington, D.C.: The National Academies Press. ISBN 0-309-14588-0. "(p1)... there is a strong, credible body of evidence, based on multiple lines of research, documenting that climate is changing and that these changes are in large part caused by human activities. While much remains to be learned, the core phenomenon, scientific questions, and hypotheses have been examined thoroughly and have stood firm in the face of serious scientific debate and careful evaluation of alternative explanations. ***(p21-22) Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities." 
  4. Andersen, Hannah; Hepburn, Brian (2015-11-13). "Scientific Method". Stanford Encyclopedia of Philosophy. Among the activities often identified as characteristic of science are systematic observation and experimentation, inductive and deductive reasoning, and the formation and testing of hypotheses and theories.
  5. Change, NASA Global Climate. "What Is the Sun's Role in Climate Change?". Climate Change: Vital Signs of the Planet. Retrieved 2022-08-14.
  6. "Major sea-level rise caused by melting of Greenland ice cap is 'now inevitable'". the Guardian. 2022-08-29. Retrieved 2022-09-20.