An opinion writer (a retired judge) asked a few questions in his Galesburg, IL local paper, and I'll provide some answers here. As always, I encourage you to read the original.
The good judge, like the usually informative Mr. Krauthammer, starts off on a very wrong foot, with bad philosophy of science. There are many facts in science -- the earth is round, the sun is hot, there is a greenhouse effect, and CO2 is a greenhouse gas. All can be questioned -- but not in the trivial way that Bulkeley and Krauthammer seem to think. 'I question it' is trivial, and pointless. If you have a _scientific_ question about these things, or any other, it is because, and only because, you have scientific evidence that the 'fact' is false.
Climate change, as even commenters in agreement with Bulkeley note, is indeed a fact. Climate changes, that's a fact. One of the tasks of science is to try to understand the hows and whys of that fact.
Let's see about the questions:
1) Average temperature has indeed gone up the past 15 years. This is a question, apparently, because the author didn't bother to look at the data. One can experiment with time periods and trends at NOAA/NCDC.
It's worth paying attention to the fact that climate trends are defined on 30 year periods, not 15. Some discussion of why this is the case is at
2) 'is global warming bad?'. Well, that'll depend on who you are and where you are, and what you rely on. If you're a poor person living near sea level, it'll be bad. If you own a ski mountain now and want to cover it with condos, you may well be happy. If you're a farmer, changes to temperature, humidity, and rainfall will probably make life more difficult.
But rather than investigate an answer to his question, Bulkeley goes off to doing some cherry-picking, perhaps not realizing that he's doing so. (But I dare say ignorance of the science in a scientific discussion, is no more an excuse than ignorance of the law is when you arrive in court.) There are two sorts of ice involved in discussion of 'the ice caps', and failing to keep track of them separately leads you to error. The kind he does mention is sea ice -- which is floating on the ocean, and most of which (by area) freezes and melts every year. But there is also land ice -- the huge ice sheets on Greenland and Antarctica. The ice sheets are melting, and this is contributing to sea level rise.
Sea ice, he ignores his own admonition about using a single year. Rephrased, and scientifically accurate -- Fall 2013 Arctic ice volume was 50% greater than the extreme record minimum that occurred in 2012, which places it, still, among the very lowest fall volumes on record.
But, to continue his take of looking at single years, did Fall 2013's increase continue? Well, no. March 2014 is back down to one of the lowest volumes ever seen for that month, in a tie with 2013. That 'increase' was awfully short-lived. No surprise to scientists -- weather happens. If you're interested in Arctic sea ice, an excellent place to watch is http://neven1.typepad.com/blog/
3) "if there is global warming, is it man-made?" this one does indeed have some technical issues, none of which he mentions, instead presenting readers with 'he-said she-said'. Some experts (no names) say one thing, some other (also unnamed) experts say another. And no sense given as to where the balance of opinion among experts is. It's overwhelmingly on the side that most of the warming since about 1950 is indeed to to human activity.
4) "If it is man-made, is there anything the United States can do about it?" Not so much a question for a physical scientist like myself, but I see he's got total confidence that cutting CO2 emissions would ruin the economy. Economists use models too. It's puzzling that he places absolute trust in those models, and absolute distrust in climate models. Nobody, in any case, has argued for the US to cut all CO2 emissions in a single day. Straw man.
5) "Finally, is there any chance that the rest of the world will cut their emissions?" Which he straightforwardly answers 'no'.
Myself, I don't rely on my psychic powers to know what everybody else in the world will do. He may if he wants. But that's certainly not science. Some countries, and regions of countries, are already reducing their CO2 emissions, which gives the trivial disproof of his answer.
After this he makes some freelance comments, including:
"The Earth has had higher and lower temperatures and higher levels of CO2 without being destroyed."
I've yet to encounter anybody saying that the earth would be 'destroyed'. Certainly not in science. It's routine, in a geological sense, for Galesburg to be under a mile or two of ice -- which is how it has spent most of the last 700,000 years. Perfectly routine, geologically, doesn't destroy the earth, but I dare say the residents would still not be happy with this magnitude of climate change.
Unfortunately, it does seem to be that magnitude, though opposite direction, of climate change that we are now looking at. When Galesburg was under a mile or more of ice, atmospheric CO2 levels were about 200 ppm. The melt off of that ice was accompanied by an 80 ppm increase, to 280 ppm. In the last 200 years, humans have increased it to 400 ppm. Climate is not a simple as we might like, but this is clearly a kick to the system that is not small.