I'll answer this in my usual roundabout way ...
One of the fundamental aspects of risk management is the Precautionary Principle, sometimes colloquially known as the 'gun' or 'condom' principle - it's better to have it and not need it, than need it and not have it! The precautionary principle is generally your fallback position. At any given moment in time, there are certain risks that have been identified. You can classify those risks as being major or minor, significant or insignificant, long-term or short-term and so on. But the problem you have is that your assessment of that risk is made at that particular moment in time. You do not have a magic crystal ball to foresee whether your classification is correct. Which is why you apply the precautionary principle. If you start taking action early and your risk analysis over time eventually shows that, actually, that risk is insignificant then, yes, you've spent money on trying to mitigate against something that never materialized. But you can only be certain that you actually made the wrong choice once you had sufficient data to tell you that you'd made the wrong choice. If you find the risk reduces as you get more data, then you roll back your mitigation efforts. And if the data shows your risk is increasing, then at least you've already started and can increase your efforts. What you do not do is nothing. The 'do nothing until you're certain' scenario could be the cheapest if you're right or most expensive if you're wrong depending on how your risk assessment changes over time. That's why what we actually do in just about every aspect of our lives is apply the precautionary principle ... sometimes we get it right, sometimes we get it wrong but the costs average out to be less than if we just waited to see what happened with each individual risk before we applied some mitigation strategy.
So, let's look at global warming. Jimz says he isn't particularly alarmed by a degree or two of warming. But what, exactly, is the basis for that decision on the risk? Is it simply because 1 or 2 degrees sounds insignificant? Another way of putting the risk is that global sea levels are rising by an average of about 3 mm per year. Projecting this as a linear you can say it means sea levels more than a foot higher in 2100 than in 2000. So if we now look at coastal and river flooding due to storm surges today, it seems very clear that a foot of additional water will result in greater potential for flooding in the future. Do we do nothing until we start to see definitive proof of increased probability and extent of flooding, or do we apply the precautionary principle and begin planning and work to deal with higher sea levels. If we find out we're wrong, we roll back our efforts. If we find out we're right, we've reduced the risk. If we do absolutely nothing and we were right, then we're going to have to spend lots of money dealing with the problems as they happen and still now have to spend money on the defenses. And this is just flooding. Add in other risks, and all of a sudden the 'do nothing until we're certain scenario' seems less and less a reasonable strategy since it seems very improbable that ALL of the risks identified (to greater or lesser extents) will turn out to be wrong.
So I would say that 'skeptics' are alarmist. They are basically trying to rewrite history. They are effectively saying 'we don't want to apply the tried and tested risk mitigation strategy of the precautionary principle in this case'. They then don't back that up with any solid reason as to why there are no risks associated with global warming. In fact, what some claim is that it will be beneficial. So whilst they say, on the one hand, that one or two degrees is insignificant and poses no risks, they then say actually it's significant enough to be beneficial. Their approach is alarming, disingenuous, and lacking in basic risk assessment or management thinking. What they seem to think is that we want to grab loads of cash and spend it tomorrow, rather than plan our spending in keeping with the evolving nature of the risks that are identified.