If 2015 was the warmest year on record, that has little significance. We already knew that the earth has been warming since the end of the Little Ice Age, so it's not surprising that 2015 would be the warmest year in this period. Assuming 2015 was the warmest year on record, that gives little information regarding key uncertainties of climate science, such as1. The value of climate sensitivity2. Understanding natural climate impacts3. Harms and benefits from various levels of global warming.4. Impact of global warming (if any) on other aspects of nature: windstorms, earthquakes, rainfall, etc.5. What realistic methods exist for reversing the growth of atmospheric CO2.cheers
Still denying, David? What will it take?Why was 2015 the warmest El Nino year on record, and so much warmer than 1982's El Nino and 1997's El Nino?How can one year possibly give the value of climate sensitivity (which isn't calculable anyway)?How can one year answer ANY of your questions? The trend is what's important -- that's where you'll find the answers to your questions.
David in Cal wrote:"We already knew that the earth has been warming since the end of the Little Ice Age...."Obviously. But why is it warming?
David in Cal."We already knew that the earth has been warming since the end of the Little Ice Age..."I hear that from time to time. Would you like to post a reference to back up your claim?It does beg the question - what is causing the earth to warm? And why would the rate of warming be accelerating?
David, I'm not denying anything. There are people who assert that warming has stopped or that man's activity doesn't contribute to the planet's warming. I'm not one of these people.My understanding is that the earth is warming. It's warming faster than it had been, because of man's emissions. The 2015 El Nino was warmer than the 1982 El Nino because the planet is warmer now than it was in 1982. You and I agree that one year cannot answer my questions, that the trend is what's important. Harry, termperature records show that the earth has been warming for 200+ years. Other natural changes show the warming in recent centuries. The rate of warming is accellerating because man's emissions contribute to the warming.Cheers
Good to see you David.Actually I liked this figure by Gavin even more because it uses CMIP3 and the forecast is from 2000. The temperature anomaly for 2015 puts it right smack on the average over the simulations.I would also add that it's not clear if the rate of warming is accelerating. It depends on what you're talking about. If it's surface temperatures, then you need to resist the temptation to say it's accelerating for exactly the same reason one doesn't say there is a pause. Too short a time span and you need to take into account the autocorrelation of the data. However, if you look at something like sea level rise, then it's clearer that there is an acceleration over the last 200 years. In fact there may even be a third derivative because the rate of change of the forcing is also changing.One last point. Down below in the sea surface temperature thread I laid out my prediction of what NASA would say the probability that 2015 was the warmest year. I said 95% if 1 sigma = 0.05. Gavin came in at 94%. It's clear that 0.05 is 1-sigma, not 2-sigma. It also means I have no idea how Berkeley Earth came in with a 1-sigma of 0.025.
David in Cal wrote:"termperature records show that the earth has been warming for 200+ years."What temperature records? Not HadCRUT4. Its records starts in 1850, and the surface temperature change by 1920 was -0.1 C and by 1930 was 0.0 C. By 1960 it was +0.3 C. Today it is at +0.8 C.data:http://www.metoffice.gov.uk/hadobs/hadcrut4/data/current/time_series/HadCRUT.18.104.22.168.monthly_ns_avg.txt
Gee, David. I didn't know that the end of Little Ice Age was controversial. Berkeley Earth shows temeperatures generally rising since 1750. http://berkeleyearth.org/summary-of-findings/ This reconstruction shows temperatures rising faster after 1960 or so, when man's emissions became a significant factor. The ten-year average in 1750 is about -1.0 The mean in 1960 was around -0.1. The mean today is around 0.75.Cheers
Some warming certainly occurred after the volcanic aersols that (likely) caused the LIA cleared out, and more in the first half of the 20th century from an increase in solar irradiance of appx 1 W/m2 and anthropogenic GHGs. But that warming was nothing like the trends of today, and as far as I know no one has identified any natural factors behind even part of the warming in the last half century.People like William Ruddiman think man has been influencing climate for thousands of years, by clearing land for agriculture.
David."Harry, termperature records show that the earth has been warming for 200+ years. Other natural changes show the warming in recent centuries. The rate of warming is accellerating because man's emissions contribute to the warming."Reference to the data please. You really can't just go and say "so it's not surprising that 2015 would be the warmest year in this period" and not back up that claim.I will give you a hand with one bit. The Pages 2K reconstruction etc.My issue is The Little Ice Age is ambiguous.http://www.realclimate.org/images//Marcott_PAGES2k.png
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