Are humans the main cause of global warming?

This resource is a wikidebate, a collaborative effort to gather and organize all arguments on a given issue. It is a tool of argument analysis or pro-and-con analysis. This is not a place to defend your preferred points of view, but original arguments are allowed and welcome. See the Wikidebate guidelines for more.

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?

Pro

• Pro 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.
  • 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 . 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).

Con

• Con Science shows that climate change is happening but not that it's influenced by human activity.
  • 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.
    • 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. 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?
• Con The most extensive melting of polar ice caps occurred in 2005. The second most extensive melting of polar ice caps occurred in 2016. 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.
  • Objection The melting of polar ice caps is not the only indicator of global warming. Still, polar ice caps are actually melting 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

• Should we use nuclear energy?