Thanks for the links. I'll add one link, direct to the project page, since it has links to the actual data, as well as much more detail than is in the articles:
(1) The project confirmed the data on temperature trends, but the error bar sizes are only reasonable back to about 1860; further back than that, the error bars get quite large. This is glossed over in the statements of findings: for example, the summary of findings (http://berkeleyearth.org/summary-of-findings) says: "Global land temperatures have increased by 1.5 degrees C over the past 250 years", but the error bars in 1750 are about +/- 1.5 C. You can't conclude anything reliably when the error bars are as large as the signal you think you see in the data.
(I also note, btw, that this conclusion is mis-stated in the NYT op-ed by Muller: it says "Our results show that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half degrees over the most recent 50 years". Neither of those statements are consistent with the summary of findings page on the project site, which claims, and shows, 1.5 C rise over the past 250 years, as above, and less than 1 C rise over the past 50 years.)
(2) The project looked at statistics on temperature trends to test whether the "urban heat island" effect might have biased the conclusions; since they saw the same trends when looking at rural areas only, they concluded that it didn't. But that isn't the only criticism Anthony Watts made of the individual station data: he claimed that the locations of many individual thermometers, urban and rural, were poorly chosen (the classic case is one that was placed in the hot air exhaust stream of an air conditioning unit). The Berkeley project did not go and eyeball individual stations, as Watts did, so they had no way of assessing this effect.
They used Watts own siting data and showed that both poor and good sites showed the same temperature trend over time.
The data back to 1860 are also sufficient to establish the current warming trend and through other analysis (e.g. Meehl, et al's work) to establish the climate sensitivity. Climate science as a discipline does not hinge on knowing exactly how warm it was 250 years ago within +/- 0.5C.
The data back to 1860 are also sufficient to establish the current warming trend
Only if you assume that there are no significant cyclic effects on longer time scales.
Climate science as a discipline does not hinge on knowing exactly how warm it was 250 years ago within +/- 0.5C.
It does if you're claiming, as the IPCC does based on the input of climate scientists, that temperatures now are warmer than they have been in at least several thousand years.
This is not as relevant as you're implying - if there are cyclic effects on long time scales, you're implying they're highly exponential - long periods of no warming, and then sudden periods of rapid warming (oddly correlated with the rise in human CO2 emissions at that).
There's no postulated mechanism for how this could be the case - where is the extra energy or heat retention coming from and managing to come into play so suddenly since the 1970s?
Whereas, if one accounts for anthropogenic CO2, it explains it superbly.
if there are cyclic effects on long time scales, you're implying they're highly exponential
I'm implying no such thing. Consider an analogy: I look at the temperature trend from February through May and conclude that I have enough data to show a significant warming trend. I therefore predict that by November, the planet will be dangerously overheated.
Obviously I have ignored a cyclic effect on a longer timescale. Is it "highly exponential" as you describe?
long periods of no warming, and then sudden periods of rapid warming
This is not what the data shows; at least, not if you look at all the data, not just a few selected temperature reconstructions that are questionable (at best) anyway. The data in full, looking at a number of different fields, shows a cycle with a period of about 800 to 1000 years; the last iteration of the cycle consisted of the Medieval Warm Period and the Little Ice Age, and we are nearing the next maximum of the cycle now.
This is not to say that human activities (of which CO2 emissions are only one component: why is it that nobody talks about land use?) have had no effect on the climate. (Arguably, humans terraforming the planet has been a significant factor in keeping another Ice Age from starting.) But if you're using the wrong baseline, it's tough to separate the human effects from the other effects.
Except no one is simply curve fitting the data - you haven't proposed any alternative mechanism that leads to a multi-decadal warming cycle.
That's what anthropogenic climate change is - since the only effect that suitably explains warming is increased eCO2 in the atmosphere.
Absent (effective)CO2 increases, you can't explain the warming trend. There shouldn't be one as pronounced.
If you're going to say "well what if there's a long cycle" - then well, what is it exactly? Where is all this additional heat retention in the atmosphere coming from? There are no multi-decadal phenomena on Earth which can explain the temperature record.
EDIT: The data for example, does not show a 1000 year cycle. You're inferring there's a cycle, by doing what you accuse others of - pointing to a graph, and declaring that because it looks "roughly" cyclical it is.
Absent (effective)CO2 increases, you can't explain the warming trend.
I understand that that is the "official" view of climate science, but that doesn't mean it's right. I don't think we're going to resolve that sort of dispute here, but if your only argument is from authority--"climate science says so"--then that's not enough for me. I don't think climate science as a field has exercised sufficient care to be just taken at their word.
If you're going to say "well what if there's a long cycle" - then well, what is it exactly?
Nobody knows for sure; we don't understand how the climate works well enough for that. But the fact that we don't have a theory that explains the cycle doesn't mean there isn't one.
Where is all this additional heat retention in the atmosphere coming from?
Actually, the amount of heat being retained in the atmosphere is miniscule on a planetary scale. The significant heat sink is the oceans. You have to be careful distinguishing between heat and temperature.
As for where it's coming from, as above, we don't understand all the causal factors at work; the fact that we have studied one intensively (CO2) does not mean that one must be the only significant one. (The IPCC report itself lists a number of significant causal factors as having a "low" level of scientific understanding.)
The data for example, does not show a 1000 year cycle.
Whose data? I understand that the "Hockey Stick" does not show a 1000 year cycle, but the "Hockey Stick" is not data; it's a (questionable at best) reconstruction of temperatures from data. We do not have direct temperature data from 1000 years ago, and as far as indirect data, there is plenty to indicate that there was indeed a Medieval Warm Period and a Little Ice Age, as I said.
"Only if you assume that there are no significant cyclic effects on longer time scales."
We know about cyclical effects on longer time scales like Milankovich cycles, we understand solar variation and volcanic effects. We know about the Younger Dryas and Daansgard-Oeschger cycles. We know about shorter term oscillations like the AMO and PDO.
You apparently know nothing of any of this, and have never heard of Muller's BEST study even though it was splattered all over the New York Times a few years back. Yet, you feel competent enough to make statements about how climatology isn't a real science.
We also know about something called the Dunning-Kruger effect.
you feel competent enough to make statements about how climatology isn't a real science.
I didn't say climatology wasn't a real science. I said it's not an accurate enough science to justify making policy decisions with huge consequences. Plenty of other real sciences are in the same state; that's to be expected, since it's a phase every real science has to go through in order to become accurate enough.
b) You expect us to believe that you have developed substantive critiques of a 3-year research project in 24 minutes of reading. (the delta between our post timestamps)
c) IMO whatever credibility you might have had to debate the science in detail is forfeited by your un-ironic reliance on the blog of a retired TV weather guy. EDIT: this is wrong, I confused you with another poster in this thread who had previously linked to the Watts blog. My apologies.
You expect us to believe that you have developed substantive critiques of a 3-year research project in 24 minutes of reading.
I don't expect you to "believe" anything. I expect you to look at the items I pointed out and see what you think of them. If you don't agree with them, feel free to give specific reasons why not.
your un-ironic reliance on the blog of a retired TV weather guy.
I didn't bring Watts into it; the Berkeley project did. I was merely commenting on something that Watts had emphasized but I didn't see mention of in the first set of links (lamontcg gave another link that does deal with that specific issue, I'll take a look at it).
"I expect you to look at the items I pointed out and see what you think of them. If you don't agree with them, feel free to give specific reasons why not."
You need to do some research first. The fact that you had never heard of the BEST study indicates that you don't know the most superficial details about climate science and this debate (and ones that were splattered across the New York Times). I'm not going to do the work to educate you. I expect YOU to do research before you demand me to produce a 250-paper annotated bibliography of climate science and its justification. Come back when you can explain the radiative physics behind CO2 being a greenhouse gas and how it can be shown in a table-top experiment, and when you know what Milankovich cycles are. Explain what caused the last Ice Age to end, be prepared to discuss the PETM. Explain the theories behind the warming that led up to the Eocene optimum 49 million years ago and the subsequent cooling after that. Climate science is more than just arguing about anthropogenic global warming. If you want a place to start, go here:
Climate science is more than just arguing about anthropogenic global warming.
I entirely agree; but to the extent that climate science is being used to justify policy decisions with huge consequences, it is about anthropogenic global warming, since that's what the political debate is about.
Reference, please?