These are problems where what is individually rational leads to a collectively undesirable outcome. Small things that many of us do, often on a daily basis, can have disastrous consequences in aggregate. The most challenging problems humanity is facing are in one way or another collective action problems.
What problems such as these have in common is that they cannot be resolved by any political actor on their own. What is needed are either global, coordinated policy responses by states, international organisations or alliances of states; alternatively mass individual cooperation.
The list of global collective action problems is long: antibiotic resistance, plastic pollution of our oceans and waterways; the heightened concentration of greenhouse gases in the atmosphere leading to global warming; and the consumption of meat, the production of which is tied to environmental degradation.
The paradox of collective action is that while none of us can individually make a difference to the overall outcome, together we can. And while no individual’s failure to act will undermine the success of the collective effort, if too many people continue with business as usual we will not make a change for the better.
If an action of mine does not make a perceptible difference to an outcome then I cannot be morally required to perform it (or to refrain from performing it).