The Wall Street Journal letter by 16 "prominent scientists" has already provoked a question here ( Are the 16 scientists who claim that climate change is not something to worry about climate scientists? ). This question focussed on the credibility of the people writing the letter.

What about their actual arguments? Which of these three claims from their letter is or isn't a credible statement?

Candidates should understand that the oft-repeated claim that nearly all scientists demand that something dramatic be done to stop global warming is not true. In fact, a large and growing number of distinguished scientists and engineers do not agree that drastic actions on global warming are needed...

...Perhaps the most inconvenient fact is the lack of global warming for well over 10 years now. This is known to the warming establishment, as one can see from the 2009 "Climategate" email of climate scientist Kevin Trenberth: "The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't."...

...plants and animals evolved when CO2 concentrations were about 10 times larger than they are today...

...Even if one accepts the inflated climate forecasts of the IPCC, aggressive greenhouse-gas control policies are not justified economically...

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    In today's WSJ, a bit of advice from scientists: Check With Climate Scientists for Views on Climate online.wsj.com/article/… What's the relevance of the economics tag here? The denial starts BEFORE the diatribe gets to the 'it'll be too expensive to fix' part. We should kill one chicjken at a time.
    – user951
    Feb 2 '12 at 0:32
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    @WayfaringStranger Thanks for linking to this beautiful, beautiful piece. It was a joy to read. Feb 2 '12 at 15:18
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    @WayfaringStranger Economics is relevant because even if the IPCC forecasts are right, it is not obvious that avoiding warming is better than adapting to it. This is an economic judgement not a scientific one.
    – matt_black
    Feb 2 '12 at 15:42
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    Economics only becomes relevant IF the scientific consensus is correct. Since these guys are bucking the consensus they need to be FAR more explicit about their "even if the IPCC is right..." Which parts are they conceding? Otherwise they're just trying to shift an essentially scientific argument onto economic grounds, where they feel perhaps, the advantage is theirs. That's not a valid technique. It's misdirection and ass-covering. They've set themselves up to demur by saying 'this is just a fantasy anyway'.
    – user951
    Feb 2 '12 at 16:17
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    @vartex: The former director of the Institute for the Study of the Earth is a geochemist, the journal of forecasting is about economic forecasting, and the "Royal Dutch Meteorological Service" person is specialized in turbulence and aeronotical engineering. Of the 16 people, only 2 could be said to have any real expertise in the area, and both are members of fossil fuel industry-funded think tanks. Even if they weren't, you could find more than two such outliers in any field on any subject. Jul 22 '16 at 13:32

Skeptical Science has an excellent point-by-point response to the WSJ letter.

I would really like to highlight Skeptical Science's wonderful "escalator" graphic illustrating the difference between the long-term trend and short-term variation: "Skeptics" vs Realists

As we can see, looking at the whole data set rather than a carefully selected subset, the upwards trend continues unabated.

If you read Trenberth's email, you'll see that he was, at the point that they quoted from, was discussing his paper An imperative for climate change planning: tracking Earth’s global energy.

Energy can be neither created nor destroyed. Satellites observe more energy coming into the Earth's atmosphere than is leaving. And yet, despite a relatively constant buildup in energy in the Earth system, the temperature rise isn't constant, there's a lot of natural variability. Trenberth isn't happy with just categorising this as "natural variability".

It is not a sufficient explanation to say that a cool year is due to natural variability. Similarly, common arguments of skeptics that the late 20th century warming is a recovery from the Little Ice Age or has other natural origins are inadequate, as they do not provide the physical mechanisms involved. There must be a physical explanation, whether natural or anthropogenic. If surface warming occurs while the deep ocean becomes cooler, then we should be able to see the evidence.

Trenberth then goes about documenting the movement of energy amongst the parts of the Earth's various systems. However, current observation networks, in particular a shortage of deep ocean buoy coverage, mean that there is not sufficient data available for Trenberth to document where all the heat is going.

Many components of the Earth system play some role, and their monitoring is improving but falls short of what is required... Hence observations need to be taken in ways that satisfy the Global Climate Observing System climate monitoring principles and ensure long-term continuity and that have the ability to discern small but persistent signals.

Subsequent papers, incidentally, such as von Schuckmann et. al. 2009, indeed, support this suggestion, showing that deeper waters are, in fact, sequestering more heat than previous expected. Even without that - Trenberth wants to collect data that would allow a potential falsification test and to allow medium-term variability to be better understood. Good things to aim for in my view - and certainly not a basis for claims that global warming has stopped.

It is true that plants and animals did originally evolve at a time when CO2 levels were much higher. However, at the time the temperature of the Earth was also much higher. And under such a high-temperature regime, giant reptiles were able to wander the Earth eating everything. It's a long way to go from saying "plants and animals evolved when CO2 concentrations were about 10 times larger" to saying "it would be neat idea to recreate those conditions".

More testably, this is wrapped up in an argument that increased CO2 levels would be good for crop production - that plants can be grown in greenhouses under increased levels of carbon dioxide. This is true as far as it goes, but is a vast oversimplification. Some crops may do well, but there are limiting factors other than carbon dioxide. Climate change can negatively affect the availability of nutrients and moisture, as well as inducing heat stress - which will cause reductions in crop growth [1] [2] [3].

Meanwhile, scientists have studied the effects of increased CO2 availability on open-air plants - a much more realistic test.

Leakey et. al. (2009):

FACE on the other hand, which allows treatment of plants under field conditions at a realistic scale, has provided an important reality check. It has both shown where hypotheses developed in controlled environments do or do not apply, as well as insights into the mechanisms that may cause the difference. Overwhelmingly, this has shown that data from laboratory and chamber experiments systematically overestimate the yields of the major food crops, yet may underestimate the biomass production of trees.

Long et. al. (2006):

The CO2 fertilization factors used in models to project future yields were derived from enclosure studies conducted approximately 20 years ago. Free-air concentration enrichment (FACE) technology has now facilitated large-scale trials of the major grain crops at elevated [CO2] under fully open-air field conditions. In those trials, elevated [CO2] enhanced yield by ∼50% less than in enclosure studies. This casts serious doubt on projections that rising [CO2] will fully offset losses due to climate change.

The final claim in the question was the claim that aggressive controls are not economically justified, for which they cite research by economist William Nordhaus. However, when journalist Andy Revkin actually contacted Nordhaus to see what he thought of the conclusions being attributed him, here's what Nordhaus had to say:

The piece completely misrepresented my work. My work has long taken the view that policies to slow global warming would have net economic benefits, in the trillion of dollars of present value. This is true going back to work in the early 1990s (MIT Press, Yale Press, Science, PNAS, among others). I have advocated a carbon tax for many years as the best way to attack the issue. I can only assume they either completely ignorant of the economics on the issue or are willfully misstating my findings.

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    The animated chart is great fun but a poor scientific response since the trend line in the canonical version shows no error bars (actually neither does the raw data despite it being a model-based estimation of global temperature) despite it being highly sensitive to the choice of start and end point and inherent errors in the original data. In other words, nice rhetoric, bad statistics.
    – matt_black
    Feb 3 '12 at 0:16
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    That's a bit beyond the point of it: it's an illustration of the difference between short-term variation and the long-term trend. It nicely makes your point - about the claims made by the scientists who wrote the letter. A few of your criticisms are very similar to those made recently by William Briggs, which were well answered by Phil Plait.
    – Jivlain
    Feb 3 '12 at 1:02
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    -1 for animated chart. Funny how data starts in 1973, completely ignoring period of cooling from 1940s to 1970s.
    – vartec
    Feb 3 '12 at 13:39
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    @vartec: Here's a version since 1940.
    – Jivlain
    Feb 3 '12 at 22:57
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    @vartec: Have there been any questions on Skeptics on whether climate scientists have arbitrarily picked starting dates for their graphs? Feb 4 '12 at 1:16

There is no documentation to the claim that "In fact, a large and growing number of distinguished scientists and engineers do not agree that drastic actions on global warming are needed…" this is asserted often, but I have never seen any indication of this and certainly no data to back it up. There is no attempt to set parameters for what "drastic action" would consist of, or how one would gauge which scientists supported "drastic actions" and which didn't.

the second statement is the main argument against ACC theory these days. specifically because current temps are at the low end of what GCM have suggested. Here is a good discussion of important factors in this assertions with relevant links that discuss a rather complicated issue http://www.realclimate.org/index.php/archives/category/climate-science/climate-modelling/ Basically there are numerous aspects of natural variability that have trended negative recently. Solar radiation has been extremely low http://solarscience.msfc.nasa.gov/predict.shtml ENSO cycle has trended negative this past decade http://ggweather.com/enso/oni.htm and aerosol pollution in Asia has increased tremendously limiting absorption of solar radiation and possibly affecting weather patterns. http://www.sciencedaily.com/releases/2014/04/140414154412.htm

as pointed out very clearly in the above answer Trenbeth's quote is taken out of context, and recent argo data supports his conjecture that oceans must be storing excess heat due to CO2 http://ceres.larc.nasa.gov/documents/STM/2013-10/14_Global_averages.pdf

None of this empirical data proves that the recent lack of warming ( which is already extremely high for the last 1,500 years), is explained by natural cause, but the explanations are completely reasonable and not post hoc attempts to shore up a failing theory as the authors imply.

the next point about plants and CO2/temps is adequately dealt with by Jivlain's answer

the last point "...Even if one accepts the inflated climate forecasts of the IPCC, aggressive greenhouse-gas control policies are not justified economically…" is once again a subjective assertion. The IPCC policy summary http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf the recent NCA report http://nca2014.globalchange.gov and numerous other research suggests that there is a real possibility of serious damage to both the biosphere as well as economical and humanitarian effects on people in the coming decades, Recently the dissenting economic voice on the IPCC, Richard Tol was discovered to have falsely attributed positive effects of climate change in the short and medium turn do to misreading research data. http://bit.ly/1wnq1te his views ran counter to the mainstream economic analysis, and while they still do, are not nearly the optimistic note that initially was attributed to his results.

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