Why do I believe in climate change?

Question

I hear from some of my friends, family, and other people whose opinion I generally respect that the Earth's climate is either not changing or that climate change is part of the Earth's natural climate variability. (Not the same person, obviously. You can't have it both ways.)

Before I can convince them that they're mistaken, I want help understanding why I do believe in anthropogenic climate change.

It seems to me that the long time scales on which the climate operates makes the concept of human-caused climate change unintuitive. We should, therefore, require a preponderance of evidence to believe such a claim.

Here are the reasons I believe the climate is changing and the most rational objections I could think of to each of these:

R1) I have read the IPCC report on climate change and some of the primary scientific publications and find them very compelling.

O1) I am college educated, but not a climate scientist or statistician. I am not qualified to judge whether or not the measurements were taken correctly, the analysis methods are sound, or if the conclusions drawn from the analysis are reasonable.

R2) I understand there is a general scientific consensus that the climate is changing due to human activity.

O2) I don't actually know any climate scientists. So my information here is entirely 2nd hand at best.

R3) I read/hear in the news interviews with climate scientists who say the climate is changing.

O3) A handful of climate scientists does not a consensus make.

R4) I read/hear in the news about the consensus of climate scientists from reputable journalists who do know climate scientists and have interviewed and surveyed many of them.

O4) This is selection bias from the types of news programs I choose to listen to. Other news programs interview climate scientists and other 'experts' who say there is not a consensus.

R5) I see evidence of climate warming myself (glaciers retreating, longer summers, milder winters)

O5) My own observation are all anecdotal evidence and could be due to natural variability in the local climate.

Please help me to understand why it is reasonable for a lay person to believe the climate is changing.

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Edit: I am hoping that one of the following is true:

1. One of my objections is inherently irrational.
2. There is a reason that I have not listed that does not have a rational objection.

It seems to me that if all reasons for a lay person to believe in climate change have a rational objection then it follows that it is reasonable for that person to deny climate change.

Answer 1

As covered in your post, according to all the typical measures by which we --as lay people --judge science, there appears to be a solid scientific consensus that global warming exists.

However, it is true that most of us take most of science on testimony. The question for your interlocutors is what skeptical argument are they raising that doesn't apply generally to science. (How do we know the sun is a giant ball of gas at a great distance in space? How do we know nothing travels faster than light? How do we know a neutral carbon atom has four valence electrons? Most of us are not in a position to evaluate any of those claims directly.) If they are not willing to believe that all science is just a vast conspiracy, then they owe you a (non-political) explanation for why their standards of proof are so different in this one particular case.

As a side note, if you want to give them a non-scientific, intuitive argument, try this one. There's an every increasing number of people in the world, using up an increasing amount of resources and energy. It's irrational to think that can continue indefinitely without creating some kind of environmental disaster of some kind --not necessarily climate change, but something.

Answer 2

Some of the objections there don't really refute the reasoning.

Take O2: second hand evidence from a consensus of scientists is a valid reason to believe something is true. It's the value of a scientific literature review. If multiple scientists saying the same thing was not enough evidence, consensus would never matter -- but it must, because the gradual proof of theories by testing against data is how the scientific method asymptotically approaches truth.

Even further, O1 is flawed by similar reasoning. It's not the layperson's role in the scientific discussion to judge measurements -- rather, collections of people with the necessary training check the work, check the models against further data, and once everything's verified present those findings. The IPCC report is that trustable source.

...unless there's reason to doubt their findings! That, however, is a different line of reasoning. Once we're arguing about the IPCC's integrity, we're not discussing climate change but the trustworthiness of the people we trust with its investigation, and their integrity has no bearing on climate change.

Answer 3

Two common philosophical stances against stubborn skepticism are:

1. To discuss the honesty of the doubt - which is not to argue directly against the doubter as a person, but to require (in abstract) the doubt to be genuine, i. e., not just plausible, but actually existing as an affection. That stance is present in some arguments against cartesianism, for instance, and can be applied to the present case.

2. To argue that even in the absence of certainty, action is still inevitable, and so is responsibility. The refusal to take action based on lack of certainty is unjustifiable, in the same way breaking the law can't be justified by ignorance. As a consequence, doubt is not enough of a reason to proclaim "business as usual"; this attitude must have grounds of its own, and the evidence to support them.

These "strategies", so to speak, are not to be taken as a rhetorical devices. Their efficacy, as is usual in the philosophical debate, relies on a predisposition to mutual understanding.

Answer 4

The question here is when do we know when an authority is being authoritative rather than knowingly or unknowingly being misleading.

Authorities are neccessary as we all cannot be authorities on all that matters to us, as individuals or as polities.

Hence our relationship to authorities are as laymen.

Whilst we cannot learn all of climate science - we have our own lives to pursue - we can audit the authority of authorities; and here, because we're talking about science, there are ways to go about this - and you seem to have most of them covered.

For example, whilst you cannot audit the statisticians employed in Climate Science, you do know that statistics have useful ways of measuring risk, and the uncertainty in the measurement of risk.

Answer 5

The best way to see what's going on is to read carefully the climate sceptics' positions and the rebuttals. Often the sceptics' presentations are so poor it becomes obvious on which side the weight of evidence is stacked.

Edit

A case in point: "How climate change deniers’ lies made a leading sceptic change sides"