Some people think
Global warming is true,
And
If we don’t respond,
Millions of people will die,
And
This is a moral issue.
So,
Once a person accepts global warming,
Global warming becomes a moral issue?
For people who have not accepted global warming,
Global warming is not a moral issue?
I don’t think that you seem to be aware of the difference between individual subjective moral judgments and external objective moral determinations. Individual, internal moral judgments are subjective, because they change based on personal opinion. These are not to be elevated to the level of objective moral truth, which does not change based on personal opinion, and which can be determined through the study of the Natural Law.
An important reason that personal subjective moral judgments are subordinate to objective moral truth is that our understanding of objective moral truth informs and shapes how we make internal, personal moral judgments and ultimately determines whether our internal, personal moral judgments are objectively valid.
Another thing to consider is that individual freedom entitles us to make individual, internal moral judgments that affect our lives, but we do not have the right to compromise the individual freedom of others by imposing our internal, individual moral judgments in the form of objective statutes or limitations on their individual freedoms.
One of the basic tests for whether an internal, personal moral value is correct or incorrect is to determine whether the object of the moral value is morally neutral.
So…
Here’s the problem I have with your question and with your position:
Global warming, for some, may have an individual, internal, subjective moral quality. Fine, they are completely within the bounds of their freedom to have that belief.
Where they go wrong is when they decide that their individual, internal, subjective moral is an externally valid and objective moral truth which gives them the moral authority to compel others to avoid or engage in particular behaviors.
The reason that this is wrong is because, as moral agents, we assume moral responsibility for taking public action in accord with externally valid and objective moral truth. We do this all the time by enforcing punishment for violations agains the objective moral value of human life, which can occur in the commission of a murder, for example. Murder violates an objective moral value (human life), with an identifiable moral agent (the murderer), and a clearly defined outcome (death of the person murdered) that can be objectively determined.
Now hold that thought…
Something like “Global Warming” does not meet the basic conditions to be an objective moral truth because it does not reflect an objective moral value, it does not have an objectively identifiable moral agent, and it does not have a clearly defined outcome.
We simply don’t know enough about what global warming is, whether it exists, what causes it, whether it is the normal progression of natural events, whether our efforts will stop it, whether stopping it will cause worse problems, whether our efforts to stop it will make it worse, whether our efforts to stop it will cause unintended consequences in other areas of natural sciences, and so on.
Therefore, the erroneous elevation of something like “Global Warming” to the level of an objective moral truth necessarily results in the moral question “what ought we do about global warming,” and thus compels us, as moral agents, to take action.
But, as I just stated, we cannot take moral action in response to “Global warming” because we cannot objectively determine the moral agents, the causes, or the outcomes- neither can we determine with sufficient confidence the objective morality of the consequences of our actions, whether our actions will be effective, and what negative consequences may result from our attempts to take action.
So, even if someone really really believes that global warming exists and that it is bad, their feelings have no bearing on whether global warming has an objective moral quality.
Does any of this make sense to you? Or are you just going to restate your question with a new set of random line breaks?