Spencer on IPCC admission on climate feedbacks

1 11 2009

In Their Own Words: The IPCC on Climate Feedbacks

by Roy W. Spencer, Ph. D.

feedback_system

Despite the fact that the magnitude of anthropogenic global warming depends mostly upon the strengths of feedbacks in the climate system, there is no known way to actually measure those feedbacks from observational data.

The IPCC has admitted as much on p. 640 of the IPCC AR4 report, at the end of section 8.6, which is entitled “Climate Sensitivity and Feedbacks”:

“A number of diagnostic tests have been proposed…but few of them have been applied to a majority of the models currently in use. Moreover, it is not yet clear which tests are critical for constraining future projections (of warming). Consequently, a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed.”

This is a rather amazing admission. Of course, since these statements are lost in a sea of favorable (but likely superfluous) comparisons between the models and various aspects of today’s climate system, one gets the impression that the 99% of the IPCC’s statements that are supportive of the climate models far outweighs the 1% that might cast doubt. Read the rest of this entry »


Comments : 96 Comments »

Categories : modeling

Scientists Develop New Method to Quantify Climate Modeling Uncertainty

22 10 2009

(From PhysOrg.com h/t to Leif Svalgaard )– Climate scientists recognize that climate modeling projections include a significant level of uncertainty. A team of researchers using computing facilities at Oak Ridge National Laboratory has identified a new method for quantifying this uncertainty.

Photo: Martin Koser of Denmark

Photo: Martin Koser of Denmark

The new approach suggests that the range of uncertainty in climate projections may be greater than previously assumed. One consequence is the possibility of greater warming and more heat waves later in the century under the Intergovernmental Panel on Climate Change’s (IPCC) high fossil fuel use scenario.

The team performed an ensemble of computer “runs” using one of the most comprehensive climate models–the Community Climate System Model version 3, developed by the National Center for Atmospheric Research (NCAR)–on each of three IPCC scenarios. The first IPCC scenario, known as A1F1, assumes high global economic growth and continued heavy reliance on fossil fuels for the remainder of the century. The second scenario, known as B1, assumes a major move away from fossil fuels toward alternative and renewable energy as the century progresses. The third scenario, known as A2, is a middling scenario, with less even economic growth and some adoption of alternative and renewable energy sources as the century unfolds. Read the rest of this entry »


Comments : 104 Comments »

Categories : modeling

Study: model in good agreement with satellite temperature data – suggest cooling

20 10 2009

TREND ANALYSIS OF SATELLITE GLOBAL TEMPERATURE DATA

Craig Loehle
National Council for Air and Stream Improvement, Inc.
Reprint available from NCASI (PDF)

Abstract

Global satellite data is analyzed for temperature trends for the period January 1979 through June 2009.  Beginning and ending segments show a cooling trend, while the middle segment evinces a warming trend.  The past 12 to 13 years show cooling using both satellite  data sets, with lower confidence limits that do not exclude a negative trend until 16 to 22 years.  It is shown that several published studies have predicted cooling in this time frame.  One of these models is extrapolated from its 2000 calibration end date and shows a good match to the satellite data, with a projection of continued cooling for several more decades.

Figure 6.     Linear plus period model from Klyashtorin and Lyubushin (2003) overlaid on satellite data after intercept shift.  Dotted line is model extrapolation post-2000 calibration period end. a) UAH.  b) RSS.

a - UAH data plus model

Figure 6a - UAH data plus model

Read the rest of this entry »


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Categories : climate data, forecasting, modeling

Fixing the nitrogen cycle in climate modeling

12 10 2009

From a press release of Oak Ridge National Laboratory.

Key new ingredient in climate model refines global predictions

http://www.windows.ucar.edu/earth/climate/images/nitrogencycle.jpg

Nitrogen cycle - image courtesy UCAR

OAK RIDGE, Tenn., Oct. 9, 2009 — For the first time, climate scientists from across the country have successfully incorporated the nitrogen cycle into global simulations for climate change, questioning previous assumptions regarding carbon feedback and potentially helping to refine model forecasts about global warming.

The results of the experiment at the Department of Energy’s Oak Ridge National Laboratory and at the National Center for Atmospheric Research are published in the current issue of Biogeosciences. They illustrate the complexity of climate modeling by demonstrating how natural processes still have a strong effect on the carbon cycle and climate simulations. In this case, scientists found that the rate of climate change over the next century could be higher than previously anticipated when the requirement of plant nutrients are included in the climate model. Read the rest of this entry »


Comments : 118 Comments »

Categories : earth, modeling

Spencer on finding a new climate sensitivity marker

4 10 2009

The Search for a Short Term Marker of Long Term Climate Sensitivity

By Dr. Roy Spencer. October 4th, 2009

[This is an update on research progress we have made into determining just how sensitive the climate system is to increasing atmospheric greenhouse gas concentrations.]

Climate_marker

While published studies are beginning to suggest that net feedbacks in the climate system could be negative for year-to-year variations (e.g., our 2007 paper, and the new study by Lindzen and Choi, 2009), there remains the question of whether the same can be said of long-term climate sensitivity (and therefore, of the strength of future global warming).

Even if we find observational evidence of an insensitive climate system for year-to-year fluctuations in the climate system, it could be that the system’s long term response to more carbon dioxide is very sensitive. I’m not saying I believe that is the case – I don’t – but it is possible. This question of a potentially large difference in short-term and long-term responses of the climate system has been bothering me for many months.

Significantly, as far as I know, the climate modelers have not yet demonstrated that there is any short-term behavior in their models which is also a good predictor of how much global warming those models project for our future. It needs to be something we can measure, something we can test with real observations. Just because all of the models behave more-or-less like the real climate system does not mean the range of warming they produce encompasses the truth. Read the rest of this entry »


Comments : 332 Comments »

Categories : Climate News, modeling

Tornado Threat Increases as Gulf Hurricanes Get Larger

11 09 2009
Hurricane Ike

The study predicted exactly the number of tornadoes seen for Hurricane Ike, 33. (Photo courtesy: NOAA)

There have been lots of claims about hurricanes since Katrina, many of them linking “global warming” to hurricane frequency, which is of course flat wrong.

This study however is in my opinion, probable in its method and results. It is well known that hurricanes spawn tornadoes, lots of them. Creating a tool to predict how many from hurricane size and intensity is a valuable contribution to both meteorology and public safety. – Anthony

From the Georgia Tech Newsroom:

Tornado Threat Increases as Gulf Hurricanes Get Larger

Atlanta (September 8, 2009) —Tornadoes that occur from hurricanes moving inland from the Gulf Coast are increasing in frequency, according to researchers at the Georgia Institute of Technology. This increase seems to reflect the increase in size and frequency among large hurricanes that make landfall from the Gulf of Mexico. The findings can be found in Geophysical Research Letters online and in print in the September 3, 2009 issue.

“As the size of landfalling hurricanes from the Gulf of Mexico increases, we’re seeing more tornadoes than we did in the past that can occur up to two days and several hundred miles inland from the landfall location,” said James Belanger, doctoral student in the School of Earth and Atmospheric Sciences at Georgia Tech and lead author of the paper.

Currently, it’s well known that when hurricanes hit land, there’s a risk that tornadoes may form in the area. Until now, no one has quantified that risk because observations of tornadoes were too sporadic prior to the installation of the NEXRAD Doppler Radar Network in 1995. Belanger along with co-authors Judith Curry, professor and chair of the School of Earth and Atmospheric Sciences at Tech and research scientist Carlos Hoyos, decided to see if they could create a model using the more reliable tornado record that’s existed since 1995. Read the rest of this entry »


Comments : 41 Comments »

Categories : forecasting, hurricanes, modeling, weather

German Climate Adviser who says “the West’s carbon quotas are used up” once co-authored a paper saying climate models are flawed and that “global warming is also overestimated by the models”

7 09 2009

Hans Joachim Schellnhuber

Yesterday on WUWT,  a post from Luboš Motl told us how climate science has been proposed as a vehicle for wealth redistribution by Hans Joachim Schellnhuber who is the director of the Potsdam Institute for Climate Impact Research and the main German government’s climate protection adviser. Interestingly it has been discovered that he co-authored a paper critical of Global Climate Models (GCM’s) in 2001. The paper and list of co-authors is below.

Global Climate Models Violate Scaling of the Observed Atmospheric Variability (link to PDF here)

R. B. Govindan,1,2 Dmitry Vyushin,1,2 Armin Bunde,2,* Stephen Brenner,3
Shlomo Havlin,1 and Hans-Joachim Schellnhuber4
1Minerva Center and Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel
2Institut für Theoretische Physik III, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
3Department of Geography, Bar-Ilan University, Ramat-Gan 52900, Israel
4Potsdam Institute for Climate Impact Research, D-14412 Potsdam, Germany
(Received 1 November 2001; revised manuscript received 22 April 2002; published 21 June 2002)

Abstract: Read the rest of this entry »


Comments : 71 Comments »

Categories : Carbon dioxide, modeling, politics

NASA powers up for the next UN IPCC

24 08 2009
Goddard Space Flight Center recently added 4,128 processors to its Discover high end computing system, with another 4,128 processors to follow this fall.

Goddard Space Flight Center recently added 4,128 processors to its Discover high-end computing system, with another 4,128 processors to follow this fall. The expanded Discover will host NASA’s climate simulations for the Intergovernmental Panel on Climate Change. Credit: NASA/Pat Izzo

From NASA,  new fossil fuel powered toys for the boys.

Related:  “Giant sucking sound” heard in Greenbelt, MD when the switch was thrown.

Remember the day you got a brand-new computer? Applications snapped open, processes that once took minutes finished in seconds, and graphics and animation flowed as smoothly as TV video. But several months and many new applications later, the bloom fell off the rose.

Your lightning-fast computer no longer was fast. You needed more memory and faster processors to handle the gigabytes of new files now embedded in your machine.

Climate scientists can relate.

They, too, need more powerful computers to process the sophisticated computer models used in climate forecasts. Such an expanded capability is now being developed at NASA’s Goddard Space Flight Center in Greenbelt, Md.

High-End Computing System Installed

In August, Goddard added 4,128 new-generation Intel “Nehalem” processors to its Discover high-end computing system. The upgraded Discover will serve as the centerpiece of a new climate simulation capability at Goddard. Discover will host NASA’s modeling contributions to the Intergovernmental Panel on Climate Change (IPCC), the leading scientific organization for assessing climate change, and other national and international climate initiatives.

To further enhance Discover’s capabilities, Goddard will install another 4,128 Nehalem processors in the fall, bringing Discover to 15,160 processors.

“We are the first high-end computing site in the United States to install Nehalem processors dedicated to climate research,” said Phil Webster, chief of Goddard’s Computational and Information Sciences and Technology Office (CISTO). “This new computing system represents a dramatic step forward in performance for climate simulations.”
Read the rest of this entry »


Comments : 126 Comments »

Categories : Technology, modeling

Mann hockey-sticks hurricanes: Hurricanes in the Atlantic are more frequent than at any time in the last 1,000 years

13 08 2009
Michael_Mann_hurricane_matrix

Michael Mann: “This tells us these reconstructions are very likely meaningful,”

Just when you think it couldn’t get any more bizarre in Mann-world, out comes a new paper in Nature hawking hurricane frequency by proxy analysis. I guess Dr. Mann missed seeing the work of National Hurricane Center’s lead scientist, Chris Landsea which we highlighted a couple of days ago on WUWT: NOAA: More tropical storms counted due to better observational tools, wider reporting. Greenhouse warming not involved.

Mann is using “overwash” silt and sand as his new proxy. Chris Landsea disagrees in the Houston Chronicle interview saying: “The paper comes to very erroneous conclusions because of using improper data and illogical techniques,”

From the BBC and the Houston Chronicle, some excerpts are below. Read the rest of this entry »


Comments : 219 Comments »

Categories : Science, hurricanes, modeling

Evidence that Global Temperature Trends Have Been Overstated

13 08 2009

Evidence that Global Temperature Trends Have Been Overstated

Dr. Pielke has a new paper, and asked if I’d help “get the word out” I’m happy to oblige – Anthony

http://2.bp.blogspot.com/_0ZFCv_xbfPo/SjLngoV_3EI/AAAAAAAAAAY/z-orcqLuYJ4/S220/blogpic.JPG

Guest post by Dr. Roger Pielke Jr

I am a co-author on a paper that has just been accepted by the Journal of Geophysical Research-Atmospheres and is now in press (PDF here). I will add a link to a version on my personal page as soon as it is up. The paper originated in a “dinner table debate” between me and my father. It subsequently turned into a research paper involving a collaboration with Phil Klotzbach of CSU and John Christy and Dick McNider at the University of Alabama-Huntsville.

The paper is important for two reasons. First, it provides confirmatory evidence that the globe has indeed been warming over the period of the satellite records. Indeed the argument that we make in the paper depends upon the presence of a warming trend, Second, it provides a parsimonious and logical explanation for a discrepancy observed in the temperature record that has been often highlighted but which to date been unsatisfactorily explained.

For several years my father has been talking about the possibility of a “warm bias” in the surface temperature record.


Comments : 90 Comments »

Categories : climate data, modeling

How Sensitive is the Earth’s Climate?

8 08 2009

Guest Post By Steve Fitzpatrick

Fitzpatrick_Image1

Introduction

Projections of climate warming from global circulation models (GCM’s) are based on high sensitivity for the Earth’s climate to radiative forcing from well mixed greenhouse gases (WMGG’s).  This high sensitivity depends mainly on three assumptions:

1. Slow heat accumulation in the world’s oceans delays the appearance of the full effect of greenhouse forcing by many (eg. >20) years.

2. Aerosols (mostly from combustion of carbon based fuels) increase the Earth’s total albedo, and have partially hidden the ‘true’ warming effect of WMGG increases.  Presumably, aerosols will not increase in the future in proportion to increases in WMGG’s, so the net increase in radiative forcing will be larger for future emissions than for past emissions.

3. Radiative forcing from WMGG’s is amplified by strong positive feedbacks due to increases in atmospheric water vapor and high cirrus clouds; in the GCM’s, these positive feedbacks approximately double the expected sensitivity to radiative forcing.

However, there is doubt about each of the above three assumptions. Read the rest of this entry »


Comments : 334 Comments »

Categories : earth, modeling

A simple analogy on climate modeling – looking for the red spot

4 08 2009

This simple visual analogy that Ron House has designed can help readers not familiar with a contentious atmospheric modeling issue get a primer on the it. While not a perfect analogy (and by definition analogies often aren’t) it does help convey an important point: the predicted red spot has not appeared. For the more technically inclined,  or for those wanting more, Steve McIntyre posted an interesting discussion at Climate Audit. – Anthony

Predicted atmospheric temperature changes from a model,showing hotspot in atmosphere above the tropics

Models predict this heating in the tropics

Guest Post by Ron House July 29, 2009

When I started looking into the claims of dangerous warming due to carbon dioxide, I was completely baffled, buried in details of climate models, puzzled by energy balance diagrams, and so forth. Was there a “greenhouse” blanketing the Earth, slowly frazzling us to death? The truth could have been anything. If you’ve followed this path too, you’ll know what I mean. But one thing, one single piece of the jigsaw, cut through all the fog and answered the question. I want to show you the thing that absolutely clinched the global warming question for me. I have postgraduate training in physics, which helped, but the basic point is understandable by anyone, and in this article I want to explain what seems to me the key, conclusive fact in everyday terms. Read the rest of this entry »

Comments : 198 Comments »

Categories : forecasting, modeling

July 24th issue of Science: Study shows clouds may exacerbate global warming with positive feedback, but there’s a caveat in the Science summary

25 07 2009

This study is being listed as proof by some of the usual alarmist types that the issue of cloud feedback is settled. Before accepting that, read this from the summary in the June 24th issue of Science by Richard A. Kerr:

The first reliable analysis of cloud behavior over past decades suggests—but falls short of proving—that clouds are strongly amplifying global warming. If that’s true, then almost all climate models have got it wrong. On page 460, climate researchers consider the two best, long-term records of cloud behavior over a rectangle of ocean that nearly spans the subtropics between Hawaii and Mexico. In a warming episode that started around 1976, ship-based data showed that cloud cover—especially low-altitude cloud layers—decreased in the study area as ocean temperatures rose and atmospheric pressure fell. One interpretation, the researchers say, is that the warming ocean was transferring heat to the overlying atmosphere, thinning out the low-lying clouds to let in more sunlight that further warmed the ocean. That’s a positive or amplifying feedback. During a cooling event in the late 1990s, both data sets recorded just the opposite changes—exactly what would happen if the same amplifying process were operating in reverse.

Here’s the press release. I’ve looked at a few news writeups on it, and the caution listed in Science about it not being proven  seems to be off the reporting radar. We’ll need further studies on a global scale, and not just one patch of ocean, before the question can be fully answered.  – Anthony

http://www.physorg.com/newman/gfx/news/hires/consultingwi.jpg

This image shows unique cloud patterns over the Pacific Ocean of the coast of Baja California, an area of great interest to Amy Clement and Robert Burgman of the University of Miami and Joel Norris of Scripps Oceanography, as they study the role of low-level clouds in climate change. Credit: NASA

From Physorg.com

The role of clouds in climate change has been a major question for decades. As the earth warms under increasing greenhouse gases, it is not known whether clouds will dissipate, letting in more of the sun’s heat energy and making the earth warm even faster, or whether cloud cover will increase, blocking the Sun’s rays and actually slowing down global warming.

In a study published in the July 24 issue of Science, researchers Amy Clement and Robert Burgman from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science and Joel Norris from Scripps Institution of Oceanography at UC San Diego begin to unravel this mystery. Using observational data collected over the last 50 years and complex climate models, the team has established that low-level stratiform appear to dissipate as the ocean warms, indicating that changes in these clouds may enhance the warming of the planet. Read the rest of this entry »


Comments : 129 Comments »

Categories : Science, climate_change, modeling

New paper from Lindzen demonstrates low climate sensitivity with observational data

23 07 2009

“…ERBE data appear to demonstrate a climate sensitivity of about 0.5°C which is easily distinguished from sensitivities given by models.”


Lindzen_ERBE_models

figure 3 - click for larger image

On the determination of climate feedbacks from ERBE data

Richard S. Lindzen and Yong-Sang Choi
Revised on July 14, 2009 for publication to Geophysical Research Letters

Abstract
Climate feedbacks are estimated from fluctuations in the outgoing radiation budget from the latest version of Earth Radiation Budget Experiment (ERBE) nonscanner data. It appears, for the entire tropics, the observed outgoing radiation fluxes increase with the increase in sea surface temperatures (SSTs). The observed behavior of radiation fluxes implies negative feedback processes associated with relatively low climate sensitivity. This is the opposite of the behavior of 11 atmospheric models forced by the same SSTs. Therefore, the models display much higher climate sensitivity than is inferred from ERBE, though it is difficult to pin down such high sensitivities with any precision. Results also show, the feedback in ERBE is mostly from shortwave radiation while the feedback in the models is mostly from longwave radiation. Although such a test does not distinguish the mechanisms, this is important since the inconsistency of climate feedbacks constitutes a very fundamental problem in climate prediction.

Introduction
The purpose of the present note is to inquire whether observations of the earth’s radiation imbalance can be used to infer feedbacks and climate sensitivity. Such an approach has, as we will see, some difficulties, but it appears that they can be overcome. This is important since most current estimates of climate sensitivity are based on global climate model (GCM) results, and these obviously need observational testing.

Read the rest of this entry »


Comments : 104 Comments »

Categories : Science, modeling

Insufficient Forcing Uncertainty

19 07 2009

insufficient-force-catIt seems depending on who you talk to, climate sensitivity is either underestimated or overestimated. In this case, a model suggests forcing is underestimated. One thing is clear, science does not yet know for certain what the true climate sensitivity to CO2 forcings is.

There is a new Paper from Tanaka et al (download here PDF) that describes how forcing uncertainty may be underestimated. Like the story of Sisyphus, an atmospheric system with negative feedbacks will roll heat back down the hill. With positive feedbacks, it gets easier to heatup the further uphill you go. The question is, which is it?

Insufficient Forcing Uncertainty Underestimates the Risk of High Climate Sensitivity

click for larger image

click for larger image

ABSTRACT

Read the rest of this entry »


Comments : 170 Comments »

Categories : Carbon dioxide, modeling

CO2, Soot, Modeling and Climate Sensitivity

15 07 2009

Warming Caused by Soot, Not CO2

From the Resilient Earth

Submitted by Doug L. Hoffman on Wed, 07/15/2009 – 13:19

A new paper in Science reports that a careful study of satellite data show the assumed cooling effect of aerosols in the atmosphere to be significantly less than previously estimated. Unfortunately, the assumed greater cooling has been used in climate models for years. In such models, the global-mean warming is determined by the balance of the radiative forcings—warming by greenhouse gases balanced against cooling by aerosols. Since a greater cooling effect has been used in climate models, the result has been to credit CO2 with a larger warming effect than it really has.

This question is of great importance to climate modelers because they have to be able to simulate the effect of GHG warming in order to accurately predict future climate change. The amount of temperature increase set into a climate model for a doubling of atmospheric CO2 is called the model’s sensitivity. As Dr. David Evans explained in a recent paper: “Yes, every emitted molecule of carbon dioxide (CO2) causes some warming—but the crucial question is how much warming do the CO2 emissions cause? If atmospheric CO2 levels doubled, would the temperature rise by 0.1°, 1.0°, or by 10.0° C?”


Temperature sensitivity scenarios from IPCC AR4.

The absorption frequencies of CO2 are already saturated, meaning that the atmosphere already captures close to 100% of the radiation at those frequencies. Read the rest of this entry »


Comments : 209 Comments »

Categories : Carbon dioxide, modeling

“There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.”

14 07 2009

Global warming: Our best guess is likely wrong

Published: Tuesday, July 14, 2009 – 11:45 in Earth & Climate
A new study suggests scientists' best predictions about global warming might be incorrect.

Rice University/Photos.com

No one knows exactly how much Earth’s climate will warm due to carbon emissions, but a new study this week suggests scientists’ best predictions about global warming might be incorrect. The study, which appears in Nature Geoscience, found that climate models explain only about half of the heating that occurred during a well-documented period of rapid global warming in Earth’s ancient past. The study, which was published online today, contains an analysis of published records from a period of rapid climatic warming about 55 million years ago known as the Palaeocene-Eocene thermal maximum, or PETM.

“In a nutshell, theoretical models cannot explain what we observe in the geological record,” said oceanographer Gerald Dickens, a co-author of the study and professor of Earth science at Rice University. “There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.” Read the rest of this entry »


Comments : 241 Comments »

Categories : Carbon dioxide, climate_change, modeling

Climate projections: Past performance no guarantee of future skill?

7 07 2009

crystal_ball2

Forecasting accuracy of Global Climate Models is something that has been at the very heart of the global warming debate for some time. Leif Svalgaard turned me on to this paper in GRL today:

Reifen, C., and R. Toumi (2009), Climate projections: Past performance no guarantee of future skill?, Geophys. Res. Lett., 36, L13704, doi:10.1029/2009GL038082.

PDF available here

It makes a very interesting point about the “stationarity” of climate feedback strengths. In a nutshell, it says that climate models break down after a time because both forcings and feedbacks don’t remain static, and the program can’t predict such changes.

Gavin Schmidt of NASA GISS says something similar in a recent interview:

The problem with climate prediction and projections going out to 2030 and 2050 is that we don’t anticipate that they can be tested in the way you can test a weather forecast. It takes about 20 years to evaluate because there is so much unforced variability in the system which we can’t predict — the chaotic component of the climate system — which is not predictable beyond two weeks, even theoretically. That is something that we can’t really get a handle on.

From Edge: THE PHYSICS THAT WE KNOW: A Conversation With Gavin Schmidt [with video]

Some excerpts from the paper: Read the rest of this entry »


Comments : 78 Comments »

Categories : climate_change, modeling

Quote Of The Week #13

6 07 2009

qotw_cropped

From Gary Strand, software engineer at the National Center for Atmospheric Research (NCAR) commenting on Climate Audit:

As a software engineer, I know that climate model software doesn’t meet the best standards available. We’ve made quite a lot of progress, but we’ve still quite a ways to go.

I’ll say. NASA GISS model E written on some of the worst FORTRAN coding ever seen  is a challenge to even get running. NASA GISTEMP is even worse. Yet our government has legislation under consideration significantly based on model output that Jim Hansen started. His 1988 speech to Congress was entirely based on model scenarios.

Do we really want congress to make trillion dollar tax decisions today based on “software [that] doesn’t meet the best standards available.”?

There’s more. Steve McIntyre comments:

Read the rest of this entry »


Comments : 164 Comments »

Categories : Quote of the Week, modeling

Common Sense and The Perils of Predictions

12 06 2009

Guest essay by Michael R. Smith, C.C.M.

PredictionsForDisaster

Forbes, “Absolute Return” column, April 21, 2008, page 246:

Here’s another name you should own, Freddie Mac ($29 per share)…Freddie is cheap at 1.1 times book [value].

Less than five months later, Freddie Mac’s stock was worth 25¢ per share, a loss of 99%.  It has since recovered to 70¢ per share, so the loss is “only” 97.6%.

A forecast of a stock of a single company five months into the future seems easy.  The company had government backing (federally sponsored corporation).  What could go wrong?

Yet, the forecast published by Forbes, short of an outright bankruptcy, could not have been more inaccurate.  It is worth examining how a situation that seemed rock solid (government-backed securities!) became catastrophic to see if there are any lessons that might apply to the atmospheric sciences.

The assumptions that Freddie Mac (and other financial stocks) were low risk was primarily a result of computer models.  As one expert stated (using pseudonym at http://blogs.zdnet.com/Murphy/?p=1265 ), Read the rest of this entry »


Comments : 80 Comments »

Categories : forecasting, modeling

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