But like I said, as a practical matter I agree with a lot that Noah has to say. He concludes with: "The solution is for macroeconomists to A) admit their ignorance more often (see this Mankiw article and this Cochrane article for good examples of how to do this), and B) search for better ways to falsify macro theories in a convincing way." Both are very good suggestions, and I'm particularly interested in B.
Some reasons why people get so down on macro (inappropriately, in my view) is:
1. They have this idealized Popperian physics in their head (is this even how physics works?) of crisp laws describing phenomena and clear cut experiments, and that's just not what defines science nor is it representative of all science. Economics is more like biology: (a.) complex processes all at work at once (so it's not clear there has to be one "right" macroeconomic theory (b.) explanation is more important than prediction, precisely because it is a complex system, and (c.) there's a whole lot of good scientific work to do that is largely descriptive or taxonomical. Physics-envy is not good for economics. We're studying the social behavior of highly evolved apes. Economists are very specialized primatologists. That should give you a hint that you should probably look to biology rather than physics for a template.
2. We expect models to explain a lot more than they were designed to explain. This problem with how people view macroeconomics is well illustrated in a recent post (quoting an older article) by Mark Thoma. He writes: "Macroeconomic models have not fared well in recent years – the models didn’t predict the financial crisis". What a fascinating sentence! Why would anyone expect a macroeconomic model to predict a financial crisis? Who says this is a determinant of whether macroeconomic models have "fared well"? Can I say that household bargaining models haven't "fared well" because they didn't predict the financial crisis? Of course not. That's silly. The financial crisis was not a macroeconomic crisis. It was not driven by macroeconomic processes. The financial crisis was caused by the vagaries of the finance industry. You judge finance models by this, not macroeconomic models. Now, how have macroeconomic models done in predicting how the macroeconomy would respond to the financial crisis? How have macroeconomic models done in explaining the path of output, interest rates, inflation, and employment? Some have certainly done more than others. None predicted a financial crisis because, well, that's what finance guys do. Should we look into macro-finance linkages? Definitely. Definitely, definitely, definitely. But the crisis was caused by the structure of CDOs, by certain risk models, by expectations about house prices, and by the exposure of different financial firms. None of these are really issues that macroeconomists are best placed to speak on.
3. Prediction may be impossible. This kind of expands on point #1. We don't say that seismologists aren't scientists because they can't predict the epicenter and magnitude earthquakes a couple years in advance. We don't say that climatologists aren't scientists because they can't predict right now when and where the hurricanes will hit next hurricane season. We don't say that evolutionary biologists aren't scientists because they can't sketch out the food chain 100 million years from now. And these failures at prediction also don't cause us to abandon the models used by seismologists, climatologists, or evolutionary biologists. Even if you get caught up in this falsification project, falsification doesn't necessarily imply prediction. Prediction of complex systems is very hard. Sometimes we can just explain the behavior of complex systems. Scientists aren't miracle-workers.