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An accurate picture of what? The "anthropogenic signal"?
All it shows is, that according to GIStemp, global mean temperature has increased by 0.88°C in the last 100 years.
The IPCC's own assessment is, that human influence became the dominant climate factor in the mid 20th century, when greenhouse gas emissions started to increase exponentially.
Naturally, the logical questions would be, how much has it warmed and how much warmer does it get in the future. Contrary to your claim, the IPCC has given very specific answers.
The right-hand panel shows ranges of global average temperature change above pre-industrial, using (i) ‘best estimate’ climate sensitivity of 3°C (black line in middle of shaded area), (ii) upper bound of likely range of climate sensitivity of 4.5°C (red line at top of shaded area) (iii) lower bound of likely range of climate sensitivity of 2°C (blue line at bottom of shaded area).
Which leads to my point that there's no set value. Temperature increase projections are a range not a set value. The observed temperature increase falls within the range of projections. Some years or decades were more dramatic, others lulled us.
IPCC Projections of Future Changes in Climate
For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected.
Model experiments show that even if all radiative forcing agents were held constant at year 2000 levels, a further warming trend would occur in the next two decades at a rate of about 0.1°C per decade, due mainly to the slow response of the oceans. About twice as much warming (0.2°C per decade) would be expected if emissions are within the range of the SRES scenarios.
It's a bit bizarre to call someone who's simply stating a truth "duplicitous", while at the same time you seem to believe it is justified to make incorrect claims and to twist the facts in your favor. Let's try to keep things honest.
What part of 'set value' vs 'about' or 'range' do you not understand?
Similarly, scientific uncertainty is hardly mentioned; when ranges are given, as in the projected temperature increases of 0.2°C to 0.5°C per decade, no probability or likelihood is assigned to explain the range (see Chapter 10).
There is close agreement of globally averaged SAT multi-model mean warming for the early 21st century for concentrations derived from the three non-mitigated IPCC Special Report on Emission Scenarios (SRES: B1, A1B and A2) scenarios (including only anthropogenic forcing) run by the AOGCMs (warming averaged for 2011 to 2030 compared to 1980 to 1999 is between +0.64°C and +0.69°C, with a range of only 0.05°C).
Thus, this warming rate is affected little by different scenario assumptions or different model sensitivities, and is consistent with that observed for the past few decades (see Chapter 3).
Possible future variations in natural forcings (e.g., a large volcanic eruption) could change those values somewhat, but about half of the early 21st-century warming is committed in the sense that it would occur even if atmospheric concentrations were held fixed at year 2000 values.
From 2000 through 2011, the Rahmstorf et al. unadjusted and adjusted trends in the observational data are 0.06 and 0.16°C per decade, respectively. While the unadjusted trend is rather low as noted above, the adjusted, underlying human-caused global warming trend is consistent with the IPCC AR4 Scenario A2 projected rate of warming of approximately 0.18°C per decade.
I've had a quick look a woodfortrees and there is one thing I am certain of: There isn't enough data in 30 years to usefully determine a trend. 30 years is basically 30 data points because a year is a complete cycle.
Originally posted by talklikeapirat
You should have taken a longer look to confirm for yourself if this the case. 30 years is exactly a period used to determine statistically significant, multidecadal temperature trends
My only contention was a one line response to a one line quote you made. You stated that the IPCC prediction was .25C increase. I stated that was wrong because there's a range.
The climate system is a complex, interactive system consisting of the atmosphere, land surface, snow and ice, oceans and other bodies of water, and living things. The atmospheric component of the climate system most obviously characterises climate; climate is often defined as ‘average weather’. Climate is usually described in terms of the mean and variability of temperature, precipitation and wind over a period of time, ranging from months to millions of years (the classical period is 30 years).
Kali, would you please cite the reference in IPCC reports where the range for the projected rate of change for global mean temperature is clearly stated.
The ars technica article you've linked to, discusses a paper published in Nature's climate change letters. Have you read the paper? If you have, do you understand how the past predictons were evaluated and how the researchers arrived at the conclusion that is summarized in the article?
Have you read Rahmstorf et al?
Have you read Rahmstorf et al? If not, how would you know if all methods and calculations used are correctly applied to the data? How do you know if their conlusions are correct?
Asthma can be a life-threatening disease if not properly managed. In 2009, 3,388 deaths were attributed to asthma. However, deaths due to asthma are rare among children. The number of deaths increases with age. In 2009, 157 children under 15 died from asthma compared to 617 adults over 85.3 Asthma is the third leading cause of hospitalization among children under the age of 15. Approximately 29 percent of all asthma hospital discharges in 2009 were in those under 15, however only 21% of the U.S. population was less than 15 years old.4 In 2009, there were approximately 774,000 emergency room visits were due to asthma in those under 15.5 Current asthma prevalence in children under 18 ranges from 5.5% in Tennessee to 18.0% in the District of Columbia.6 The annual direct health care cost of asthma is approximately $50.1 billion; indirect costs (e.g. lost productivity) add another $5.9 billion, for a total of $56.0 billion dollars.7 Asthma is one of the leading causes of school absenteeism;8 in 2008, asthma accounted for an estimated 14.4 million lost school days in children with an asthma attack in the previous year.9
Also, I'm a bit miffed, I took time to pour through FAR for you, to provide what you requested... in the spirit of a good debate and no response?
If their aim was to show that climate models can reliably predict future climate, they've failed to do so.
By taking the opposite approach, the Rahmstorf study renders the inital assumptions and conclusions of Frame et al. practically obsolete
Frame et al. both assumed and concluded that - a: "greenhouse-gas-induced warming is largely overwhelming the other forcings, which are only of secondary importance on the 20-year timescale" (in contrast, Rahmstorf et al. assume that the 'noise' created by natural variability can lead to zero, or even negative temperature trends longer than a decade); -
For the (AGW)theory to be correct, the human emission-induced global warming signal has to be linear (not the real world response to the forcing and regardless wether or not CO2 heat-trapping and re-emission follows a logarithmic function). This is also the main premise of Rahmstorf et al. and they used this as a depature point for their regression analysis.
The first thing to note are two implicit concessions:
Temperature observations are not a reliable proxy to measure increases of the total heat content in the climate system. This would be true for Land-and Sea surface temperatures, and for ocean heat content data (natural variability i.e. ENSO events strongly affect the thermocline).
First, I'm sure you're aware but for clarity sake... the climate models aren't meant to reliably predict future climate but future temperature rise
Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate.