Climate Predictions - Let's See How Accurate They Are

towermonkey wrote: Any links to last year's accuracy?

Glad you asked! Here's the past few years:

Let's start with the 2007 summary and projections for 2008 (I can't quote everything I'd like, please read the whole report for further info!):
http://data.giss.nasa.gov/gistemp/2007/

Global Predictions

The quasi-regularity of some natural climate forcing mechanisms, combined with knowledge of human-made forcings, allows projection of near-term global temperature trends with reasonably high confidence.

Solar irradiance will still be on or near its flat-bottomed minimum in 2008. Thus solar change should not contribute significantly to temperature change in 2008.

La Niña cooling in the second half of 2007 (Figure 2) is about as intense as the regional cooling associated with any La Niña of the past half century...Effect of the current La Niña on global surface temperature is likely to continue for at least the first several months of 2008. Based on sequences of Pacific Ocean surface temperature patterns in Plate 9, a next El Niño in 2009 or 2010 is perhaps the most likely timing. But whatever year it occurs, it is a pretty safe bet that the next El Niño will help carry global temperature to a significantly higher level.

Competing with the short-term solar and La Niña cooling effects is the long-term global warming effect of human-made GHGs.

Based on these considerations, it is unlikely that 2008 will be a year with truly exceptional global mean temperature. These considerations also suggest that, barring the unlikely event of a large volcanic eruption, a record global temperature clearly exceeding that of 2005 can be expected within the next 2-3 years.

In blue is the prediction for 2008, in green is the prediction for 2009-10.

What actually happened in 2008:
http://data.giss.nasa.gov/gistemp/2008/

Calendar year 2008 was the coolest year since 2000, according to the NASA Goddard Institute for Space Studies (GISS) analysis of worldwide temperature measurements, but it was still in the top ten warmest years since the start of record-keeping in 1880. Given the range of uncertainty in the measurements, the GISS team concluded that 2008 was somewhere between the seventh and the tenth warmest year on record.

Most of the world was either near normal or warmer than normal. Eastern Europe, Russia, the Arctic, and the Antarctic Peninsula were exceptionally warm (1.5 to 3.5 degrees Celsius above average). The temperature in the United States in 2008 was not much different than the 1951-1980 mean, which makes 2008 cooler than all of the previous years this decade.

Prediction: accurate

And from that same source, the prediction for 2009-2010:

Finally, in response to popular demand, we comment on the likelihood of a near-term global temperature record. Specifically, the question has been asked whether the relatively cool 2008 alters the expectation we expressed in last year's summary that a new global record was likely within the next 2-3 years (now the next 1-2 years). Response to that query requires consideration of several factors:

Natural dynamical variability: The largest contribution is the Southern Oscillation, the El Niño-La Niña cycle. Indeed, subsurface and surface tropical ocean temperatures suggest that the system is "recharged", i.e., poised, for the next El Niño, so there is a good chance that one may occur in 2009. Global temperature anomalies tend to lag tropical anomalies by 3-6 months.

Solar irradiance: The solar output remains low (Fig. 4), at the lowest level in the period since satellite measurements began in the late 1970s, and the time since the prior solar minimum is already 12 years, two years longer than the prior two cycles. However, let's assume that the solar irradiance does not recover. In that case, the negative forcing, relative to the mean solar irradiance is equivalent to seven years of CO2 increase at current growth rates. Assuming that the solar irradiance begins to recover this year, as expected, there is still some effect on the likelihood of a near-term global temperature record due to the unusually prolonged solar minimum. Because of the large thermal inertia of the ocean, the surface temperature response to the 10-12 year solar cycle lags the irradiance variation by 1-2 years. Thus, relative to the mean, i.e, the hypothetical case in which the sun had a constant average irradiance, actual solar irradiance will continue to provide a negative anomaly for the next 2-3 years.

Volcanic aerosols:Their effect in the next two years should be negligible.

Greenhouse gases: Annual growth rate of climate forcing by long-lived greenhouse gases (GHGs) slowed from a peak close to 0.05 W/m2 per year around 1980-85 to about 0.035 W/m2 in recent years due to slowdown of CH4 and CFC growth rates [ref. 6]. Resumed methane growth, if it continued in 2008 as in 2007, adds about 0.005 W/m2. From climate models and empirical analyses, this GHG forcing trend translates into a mean warming rate of ~0.15°C per decade.

Summary: The Southern Oscillation and increasing GHGs continue to be, respectively, the dominant factors affecting interannual and decadal temperature change. Solar irradiance has a non-negligible effect on global temperature [see, e.g., ref. 7, which empirically estimates a somewhat larger solar cycle effect than that estimated by others who have teased a solar effect out of data with different methods]. Given our expectation of the next El Niño beginning in 2009 or 2010, it still seems likely that a new global temperature record will be set within the next 1-2 years, despite the moderate negative effect of the reduced solar irradiance.

What actually happened in 2009:
http://www.giss.nasa.gov/research/news/20100121/

2009 was tied for the second warmest year in the modern record, a new NASA analysis of global surface temperature shows.

What actually happened in 2010:
http://www.giss.nasa.gov/research/news/20110113/

NASA's announcement this year — that 2010 ties 2005 as the warmest year in the 131-year instrumental record — made headlines. But, how much does the ranking of a single year matter? Even for a near record-breaking year like 2010 the broader context is more important than a single year. "Certainly, it is interesting that 2010 was so warm despite the presence of a La Niña and a remarkably inactive sun, two factors that have a cooling influence on the planet, but far more important than any particular year's ranking are the decadal trends," Hansen said.

Prediction: Close, but missed by 0.1°C!

I'm putting this link in b/c it also contains snow cover trends, record breaking temp trends, and extreme weather events from around the world, all things that are predicted by climatologists as well.
http://climateprogress.org/2010/07/10/n ... r-minimum/
NASA: First half of 2010 breaks the thermometer — despite “recent minimum of solar irradiance”
July 10, 2010


What does all this mean, really?

"There's always an interest in the annual temperature numbers and on a given year's ranking, but usually that misses the point," said James Hansen, the director of GISS. "There's substantial year-to-year variability of global temperature caused by the tropical El Niño-La Niña cycle. But when we average temperature over five or ten years to minimize that variability, we find that global warming is continuing unabated."

So you probably want to smack me upside the head for making you read 3 years worth of predictions and results, huh?! Let me explain my point: year-to-year trends are not so important, as Dr. Hansen states above; but, what is important is that the temps are only going up, despite the solar minimum that we're finally exiting , and that the predictions were correct, despite claims to the contrary by the skeptics (and further back that I didn't include).

The next question is: well, what's 10 years of warming mean in comparison to the last thousands of years? Is a 0.2°C/decade and 0.8°C total rise globally since 1880 really all that significant? Yes, when you consider the main driver of the current warming - increased greenhouse gases in the atmosphere. I see lots of criticisms that the climatologists don't factor in cosmic variations more critically, and I'm not sure that that criticism is well-founded. As you can see from the reports above, especially what I didn't quote, they include solar variation, aerosols, and have specific measurements of the energy added by GHGs in Watts/square meter of earth - and they are still accurately predicting the trends in global temps. Given that land clearing, cement making, and fossil fuel burning is still increasing, we can expect no leveling off of GHGs in the atmosphere anytime soon.

How much of an increase can be expected in GHGs, specifically CO2, which sticks around for the longest in the atmosphere, if we continue business as usual and don't stop extracting and burning fossil fuels?

http://www.gcrio.org/CONSEQUENCES/vol4n ... cycle.html

Suppose we were to burn up the entire fossil fuel reservoir, 5000 Gt C, over the next several centuries. What would be the likely effect on atmospheric CO2 levels and on climate?

To answer even this, reliably, one needs a realistic, mathematical model of the carbon cycle which at a minimum simulates the vertical circulation in the world's oceans and the behavior of the terrestrial biosphere, including the effects of enhanced CO2 fertilization.

The results of the more realistic carbon cycle model, shown as the solid blue and black lines in Figure 2b, indicate that exploiting all the world's reserves of coal and oil and natural gas will drive atmospheric CO2 to peak concentrations of roughly 1100 to 1200 ppm, which are about three times the levels of today.

A CO2 concentration of 1200 ppm is equivalent to slightly more than two doublings of the pre-industrial level of 280 ppm: a stable, naturally-sustained plateau that is typical of the high CO2, interglacial periods (like the present) of the last million years of Earth history. Two doublings, based on the logic given earlier, should raise the surface temperature from 3-10°C. (37.4°F - 50°F)

Rockdoc Franz wrote: And what makes hurricane prediction and accurate indicator of Climate change? Could it have something to do with ocean temperature and the fact that there are unusual cool or warm waters, neither of which exhibit a linear relationship that could be construed as due to climate change?

Whoever said that water temps will increase linearly in response to AGW?

http://www.realclimate.org/index.php/ar ... l-warming/
Hurricanes and Global Warming – Is There a Connection?
by Stefan Rahmstorf, Michael Mann, Rasmus Benestad, Gavin Schmidt, and William Connolley
2 September 2005

Due to this semi-random nature of weather, it is wrong to blame any one event such as Katrina specifically on global warming – and of course it is just as indefensible to blame Katrina on a long-term natural cycle in the climate. Yet this is not the right way to frame the question. As we have also pointed out in previous posts, we can indeed draw some important conclusions about the links between hurricane activity and global warming in a statistical sense.

The key connection is that between sea surface temperatures (we abbreviate this as SST) and the power of hurricanes. [But] SST is not the only influence on hurricane formation. Strong shear in atmospheric winds (that is, changes in wind strength and direction with height in the atmosphere above the surface), for example, inhibits development of the highly organized structure that is required for a hurricane to form. In the case of Atlantic hurricanes, the El Nino/Southern Oscillation tends to influence the vertical wind shear, and thus, in turn, the number of hurricanes that tend to form in a given year. Many other features of the process of hurricane development and strengthening, however, are closely linked to SST.

Hurricane forecast models (the same ones that were used to predict Katrina’s path) indicate a tendency for more intense (but not overall more frequent) hurricanes when they are run for climate change scenarios (Fig. 1). The key question then becomes this: Why has SST increased in the tropics? Is this increase due to global warming (which is almost certainly in large part due to human impacts on climate)? Or is this increase part of a natural cycle?

It has been asserted (for example, by the NOAA National Hurricane Center) that the recent upturn in hurricane activity is due to a natural cycle, e.g. the so-called Atlantic Multidecadal Oscillation (“AMO”). Emanuel therefore concludes in his paper that “the large upswing in the last decade is unprecedented, and probably reflects the effect of global warming.” However, caution is always warranted with very new scientific results until they have been thoroughly discussed by the community and either supported or challenged by further analyses. What about the alternative hypothesis: the contribution of anthropogenic greenhouse gases to tropical SST warming? How strong do we expect this to be? One way to estimate this is to use climate models. Driven by anthropogenic forcings, these show a warming of tropical SST in the Atlantic of about 0.2 – 0.5 ºC. Globally, SST has increased by ~0.6 ºC in the past hundred years. This mostly reflects the response to global radiative forcings, which are dominated by anthropogenic forcing over the 20th Century. Regional modes of variability, such as the AMO, largely cancel out and make a very small contribution in the global mean SST changes.

Thus, we can conclude that both a natural cycle (the AMO) and anthropogenic forcing could have made roughly equally large contributions to the warming of the tropical Atlantic over the past decades, with an exact attribution impossible so far.

But ultimately the answer to what caused Katrina is of little practical value. The current evidence strongly suggests that:
(a) hurricanes tend to become more destructive as ocean temperatures rise, and
(b) an unchecked rise in greenhouse gas concentrations will very likely increase ocean temperatures further, ultimately overwhelming any natural oscillations.
Scenarios for future global warming show tropical SST rising by a few degrees, not just tenths of a degree (see e.g. results from the Hadley Centre model and the implications for hurricanes shown in Fig. 1 above). That is the important message from science. What we need to discuss is not what caused Katrina, but the likelyhood that global warming will make hurricanes even worse in future.

There's much more in that article, and links to other articles that explain research results further. Or you can go to the Index page here and check out all the articles under Extreme Events and Ocean for even more. http://www.realclimate.org/index.php/ar ... x/#Extreme

Hurricanes:
I used Dr. Gray's numbers for the specific reason that he is a climate skeptic to highlight the message that I think is important: the science from the NOAA, and climatologists with whom he disagrees is put out as a range, like last year's 14-23. http://www.aolnews.com/2010/05/28/your- ... scorecard/ and http://www.reuters.com/article/2008/04/ ... RN20080402 What's important about that is that it highlights how conservative climatologists are in making predictions - not just for hurricanes, but also for the global temperature increases. If you look at the graph in my original post of the review of Hansen's predictions, you see Scenario A, B, and C - these are the different conditions entered into the climate models based on our future fossil fuel use. Of course they can't predict whether we will continue business as usual, or start mitigating and reducing our carbon footprint, so they plug all the scenarios in and compare them on the same graph (and if you look at what the skeptics did, they removed the more conservative, realistic Scenario B & C plots on the graph to make it look like Hansen was way off, when in fact they were misrepresenting the data - they do this all the time). Yes, the hurricane predictions have been inaccurate, but conservatively so - they have estimated more than actually occurred, which is the safer route to take when making predictions like this. When it comes to their future temps and sea level rise estimates, keeping that thought in mind should sober you: so far they have underestimated the actual changes that have occurred to date, which means that we're very likely in for worse than what they are officially calling for.

Just out of curiosity, to those of you who made the statement, "be wrong that often and get paid that much" (and they weren't wrong on the global temp predictions) - just how much do you think the scientists are making? I'm just curious as to your thoughts on this (I haven't yet been able to find exact salaries for climate scientists vs climate skeptics - I think that info would be very enlightening, especially considering that Dr. Lindzen charges $2500/hour to Exxon for appearing before Congress...).