This is a simple question if to separate firm scientific knowledge and scientific hypothesis. People do trust well established physical knowledge like mechanics, and thus, they trust physicists in every day activity. For example, aircrafts, ships, satellites, buildings in seismic zones, TV, mobile telephony, etc. is the materialized scientific knowledge. It is beyond discussion of experts and lay public that numerous physical laws deserve absolute trust. (Imagine an expert discussion on the impossibility of mobile telephony as based on the absence of electro-magnetic waves. A hundred and fifty years ago such a discussion would be absolutely reasonable.) All these physics (or scientific in a broader notation) laws are almost fully justified by laboratory experiments and other types of measurements. Because these laws are now an indispensible part of every day life people forget that this was and is the essence of scientific knowledge.
However, there are scientific topics which have no reliable scientific solutions (yet or forever) and are characterized by a higher uncertainty in both theories and experiments. In my view, these new horizons in the hard sciences, which are formulated as hypothesis, should not be presented for the broader audience (lay public) as robust scientific knowledge. They do not have robust solutions or materializations yet. When positioned as well established scientific knowledge these hypothesis ignite severe discussion between experts and lay public. They use the uncertainty gaps in experimental justification and put forward own interpretations with various applications in real life.
I would treat “global warming” (as induced by human activity) as one of such hypothesis which should be better experimentally justified. There are so many gaps in the estimates of major sinks and sources of greenhouse gases that the relative inputs in the final balance is not clear yet. Notice, I do not say that this hypothesis is not scientifically void. I just say that a Nobel Prize for it was a premature and political decision which has changed the terms of the scientific discussion.
Now we come to economics and economic experts. It is well known that economics (I do not include finances, business, etc.) is a science without experimental or observational justification. When one judges by the prediction of large scale outcomes like recessions economics does not show any result at all. (Many economists are proud of that, however.) It is in drastic contrast to the predictions of the hard sciences - we foresee that our airplane will land with a very high probability in line with actions of many physical laws, staring with Bernoulli one, which creates the lifting force. Otherwise we would never use the plane. Here the term “economic experts” comes. These are people who discuss measured macroeconomic values without any quantitative justification. That’s why I do not like the term “expert” as applied to physicists. When I hear it I usually see a round table with several economic experts discussing a problem without any solution in scientific terms. As a rule, they can explain any process or phenomena with the same words and arguments they used to explain the opposite process and phenomena two years ago. For me its enough to decide that they are worth nothing together with their words. Economic experts use a very limited agrument base to explain everything.
In turn, the possibility to explain everything attracts the lay public. People like the illusion of understanding. In many economic blogs one can observe how readers repeat the arguments from economic experts without understanding that these experts have explained nothing. Emotionally, it is better to trust experts than scientists, who usuall do not have ready answers to all questions.
As a remark. Some physicists propose a scientific revolution in economics (Bouchaud, J.-P., (2008). Economics needs scientific revolution, Nature, v.455, 30 October 2008). I would start with a simple data analysis in line with classical mechanics (Ivan O. Kitov, 2009. “Does economics need a scientific revolution?, Quantitative Finance Papers 0904.0729, arXiv.org). Actually, economic data do not match even basic requirements of physics. They are usually incompatible over time. One needs lots of efforts to recover major time series like inflation, GDP per capita, rate of unemployment, etc. (http://mechonomic.blogspot.com/).
Therefore, a researcher in the hard sciences is hardly an expert explaining all observations and usually knows what s/he knows and what s/he does not know. The latter is the matter to investigate. When a researcher works as an expert and brings to the unprepared audience (almost any place except specialed seminars, workshops, conferences, etc.) some hypothesis with a large uncertainty it usually has a negative result. At best, nobody understands and forgets.
The worst case, politicians use one of many possibilities under the higher uncertainty for their dirty profit. As an example, I recall a long discussion in the USSR about the necessity to turn nothern rivers to the Caspian sea, which had been losing water and thus area before the 1970s. The reason is clear – money and resources, i.e. power, and this project was supported by many (specially selected) experts who forecasted the sea to disapper according to their linear models. The Soviet government was ready to start. In terms of long term observations, for an inner lake oscillations is a natural regime (as was argued by many scientists, chiefly, physicists) and the Caspian sea has been growing since the 1970s and has already inundated many small villages. The conclusion - do not give any chance to politicians to use your knowledge in their interests. In other words, do not be “experts”.
In reality, it was not the strong scientific opinion but the disintegration of the Soviet Union that stopped the project. Nobody is able to stop the greater political project “global warming”.
