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I would guess that scientists are conservative in their predictions, so that they don't over-estimate effects. As new information comes in and predictions becom

I would guess that scientists are conservative in their predictions, so that they don't over-estimate effects. As new information comes in and predictions become more accurate, it's more likely to lean towards worse outcomes because the earlier predictions were already biased the other way.

credit_guy 8y ago
Look, that's a possible explanation. But are you sure you are not rationalizing? They would need to quite a bit conservative so that pretty much any new update would be towards faster warming. Here's the 2007 IPCC estimate: "For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios". [1] Now, it did appear that estimate was slightly conservative. The actual warming for the first decade according to NASA [2] was about 0.27°C. [1]https://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-projections-of.html https://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm... [2]https://climate.nasa.gov/vital-signs/global-temperature/ https://climate.nasa.gov/vital-signs/global-temperature/
- MikeHolman 8y ago
  From what you say, they underestimated by 35%. That seems like quite a conservative underestimate.
  - credit_guy 8y ago
    Well, my first link follows with this quote: "Since IPCC’s first report in 1990, assessed projections have suggested global average temperature increases between about 0.15°C and 0.3°C per decade for 1990 to 2005. This can now be compared with observed values of about 0.2°C per decade, strengthening confidence in near-term projections." But guess what. My second link, the NASA one, shows the global increase of temperature between 2001 and 2011 to be 0.03°C. The IPCC estimate was not that conservative, was it? Should I say it was aggressive by a factor of 6? Nope, I'm not saying that. What I'm saying (and what IPCC is saying) is that generally their predictions appear to be in line with the outcome, and not to be very conservative.
    - yongjik 8y ago
      > But guess what. My second link, the NASA one, shows the global increase of temperature between 2001 and 2011 to be 0.03°C. Are we looking at the same graph? Because the graph clearly shows that yearly variation of ~0.2°C is quite normal, and picking any two years separated by 10 years is basically asking for random noise. When IPCC said global temperature would increase "between about 0.15°C and 0.3°C" in 15 years, they didn't mean "between 1990 and 2005, every successive year will be between 0.01°C and 0.02°C warmer than the previous year." Nor did they mean the year 1990 and 2005 will be "average" years whose temperatures would be smack in the middle of the surrounding time period. To think otherwise shows a fundamental misunderstanding. Climate scientists are not lawyers. They usually write for people with some scientific training, who can and are willing to follow their arguments for what they are.
      - credit_guy 8y ago
        Did you consider writing the same reply to the comment I was answering to (that 0.2 is 35% lower than 0.27). Because the same argument about ranges and variations applies. Except that that comment was left at the firm conclusion that 0.2 is more conservative than 0.27, while my reply continued with the statement that I do not think the IPCC was wrong, but rather right.
- canhascodez 8y ago
  I'm not sure why you're skeptical. Scientists get a lot of flack for publishing "doom and gloom" results, even when those are accurate, and no scientist is particularly interested in overstating this effect. Also, ".27 C" is not necessarily excluded from "about .2 C": it's not sufficient to simply compare approximate figures. There's a big difference in this context between ".2 C ± .5 C" and ".2 C ± .8 C". You would need to show that the observed result is entirely outside the predicted range, including both sets of error bars. However, focusing on the temperature record is pretty disingenuous. It's been proven beyond doubt that humanity is liberating gigatonnes of fossil carbon, which is proven beyond doubt to warm the planet, specifically by 3.7 W/m^2 per doubling. The actual rate of warming and total climate sensitivity are interesting areas of research, but do not themselves have any bearing on whether that warming will happen.
- Benjammer 8y ago
  >They would need to quite a bit conservative so that pretty much any new update would be towards faster warming The new updates are subject to the exact same bias though, it's not like you should expect it to start biased and then just immediately track towards "honest" results. Think of it as slowly reducing the bias over time, not pegging a starting point and then immediately jumping to "honest" where you expect the changes to fluctuate in a normal-distribution sort of way.

credit_guy 8y ago

Look, that's a possible explanation. But are you sure you are not rationalizing? They would need to quite a bit conservative so that pretty much any new update would be towards faster warming. Here's the 2007 IPCC estimate: "For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios". [1] Now, it did appear that estimate was slightly conservative. The actual warming for the first decade according to NASA [2] was about 0.27°C. [1]https://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-projections-of.html https://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm... [2]https://climate.nasa.gov/vital-signs/global-temperature/ https://climate.nasa.gov/vital-signs/global-temperature/

MikeHolman 8y ago
From what you say, they underestimated by 35%. That seems like quite a conservative underestimate.
- credit_guy 8y ago
  Well, my first link follows with this quote: "Since IPCC’s first report in 1990, assessed projections have suggested global average temperature increases between about 0.15°C and 0.3°C per decade for 1990 to 2005. This can now be compared with observed values of about 0.2°C per decade, strengthening confidence in near-term projections." But guess what. My second link, the NASA one, shows the global increase of temperature between 2001 and 2011 to be 0.03°C. The IPCC estimate was not that conservative, was it? Should I say it was aggressive by a factor of 6? Nope, I'm not saying that. What I'm saying (and what IPCC is saying) is that generally their predictions appear to be in line with the outcome, and not to be very conservative.
  - yongjik 8y ago
    > But guess what. My second link, the NASA one, shows the global increase of temperature between 2001 and 2011 to be 0.03°C. Are we looking at the same graph? Because the graph clearly shows that yearly variation of ~0.2°C is quite normal, and picking any two years separated by 10 years is basically asking for random noise. When IPCC said global temperature would increase "between about 0.15°C and 0.3°C" in 15 years, they didn't mean "between 1990 and 2005, every successive year will be between 0.01°C and 0.02°C warmer than the previous year." Nor did they mean the year 1990 and 2005 will be "average" years whose temperatures would be smack in the middle of the surrounding time period. To think otherwise shows a fundamental misunderstanding. Climate scientists are not lawyers. They usually write for people with some scientific training, who can and are willing to follow their arguments for what they are.
    - credit_guy 8y ago
      Did you consider writing the same reply to the comment I was answering to (that 0.2 is 35% lower than 0.27). Because the same argument about ranges and variations applies. Except that that comment was left at the firm conclusion that 0.2 is more conservative than 0.27, while my reply continued with the statement that I do not think the IPCC was wrong, but rather right.
canhascodez 8y ago
I'm not sure why you're skeptical. Scientists get a lot of flack for publishing "doom and gloom" results, even when those are accurate, and no scientist is particularly interested in overstating this effect. Also, ".27 C" is not necessarily excluded from "about .2 C": it's not sufficient to simply compare approximate figures. There's a big difference in this context between ".2 C ± .5 C" and ".2 C ± .8 C". You would need to show that the observed result is entirely outside the predicted range, including both sets of error bars. However, focusing on the temperature record is pretty disingenuous. It's been proven beyond doubt that humanity is liberating gigatonnes of fossil carbon, which is proven beyond doubt to warm the planet, specifically by 3.7 W/m^2 per doubling. The actual rate of warming and total climate sensitivity are interesting areas of research, but do not themselves have any bearing on whether that warming will happen.
Benjammer 8y ago
>They would need to quite a bit conservative so that pretty much any new update would be towards faster warming The new updates are subject to the exact same bias though, it's not like you should expect it to start biased and then just immediately track towards "honest" results. Think of it as slowly reducing the bias over time, not pegging a starting point and then immediately jumping to "honest" where you expect the changes to fluctuate in a normal-distribution sort of way.