Tag Archives: forecasts

Climate scientists can restart the climate change debate & win: test the models!

Summary; Public policy about climate change has become politicized and gridlocked after 26 years of large-scale advocacy. We cannot even prepare for a repeat of past extreme weather. We can whine and bicker about who to blame. Or we can find ways to restart the debate. Here is the next of a series about the latter path, for anyone interested in walking it. Climate scientists can take an easy and potentially powerful step to build public confidence: re-run the climate models from the first 3 IPCC reports with actual data (from their future): how well did they predict global temperatures?

Trust can trump Uncertainty.”
Presentation by Leonard A Smith (Prof of Statistics, LSE), 6 February 2014.

The most important graph from the IPCC’s AR5

Figure 1.4 from the IPCC's AR5

Figure 1.4 from p131 of AR5: the observed global surface temperature anomaly relative to 1961–1990 in °C compared with the range of projections from the previous IPCC assessments. Click to enlarge.


Why the most important graph doesn’t convince the public

Last week I posted What climate scientists did wrong and why the massive climate change campaign has failed. After 26 years, one of the largest longest campaigns to influence public policy has failed to gain the support of Americans, with climate change ranking near the bottom of people’s concerns. It described the obvious reason: they failed to meet the public’s expectations for behavior of scientists warning about a global threat (i.e., a basic public relations mistake).

Let’s discuss what scientists can do to restart the debate. Let’s start with the big step: show that climate models have successfully predicted future global temperatures with reasonable accuracy.

This spaghetti graph — probably the most-cited data from the IPCC’s reports — illustrates one reason for lack of sufficient public support in America. It shows the forecasts of models run in previous IPCC reports vs. actual subsequent temperatures, with the forecasts run under various scenarios of emissions and their baselines updated. First, Edward Tufte probably would laugh at this The Visual Display of Quantitative Information — too much packed into one graph, the equivalent of a Powerpoint slide with 15 bullet points.

But there’s a more important weakness. We want to know how well the models work. That is, how well each forecast if run with a correct scenario (i.e., actual future emissions, since we’re uninterested here in predicting emissions, just temperatures). Let’s prune away all those extra lines on the spagetti graph, leaving forecasts from 1990 to now that match the actual course of emissions.

The big step: prove climate models have made successful predictions

“A genuine expert can always foretell a thing that is 500 years away easier than he can a thing that’s only 500 seconds off.”
— From Mark Twain’s A Connecticut Yankee in King Arthur’s Court.

A massive body of research describes how to validate climate models (see below), most stating that they must use “hindcasts” (predicting the past) because we do not know the temperature of future decades. Few sensible people trust hindcasts, with their ability to be (even inadvertently) tuned to work (that’s why scientists use double-blind testing for drugs where possible).

But now we know the future — the future of models run in past IPCC reports — and can test their predictive ability.

Karl Popper believed that predictions were the gold standard for testing scientific theories. The public also believes this. Countless films and TV shows focus on the moment in which scientists test their theory to see if the result matches their prediction. Climate scientists can run such tests today for global surface temperatures. This could be evidence on a scale greater than anything else they’ve done.

Model of a hurricane.

A hurricane in the Weather Research & Forecasting (WRF) Model. From NCAR/UCAR.

Testing the climate models used by the IPCC

“Probably {scientists’} most deeply held values concern predictions: they should be accurate; quantitative predictions are preferable to qualitative ones; whatever the margin of permissible error, it should be consistently satisfied in a given field; and so on.”
— Thomas Kuhn in The Structure of Scientific Revolutions (1962).

The IPCC’s scientists run projections. AR5 describes these as “the simulated response of the climate system to a scenario of future emission or concentration of greenhouse gases and aerosols … distinguished from climate predictions by their dependence on the emission/concentration/radiative forcing scenario used…”. The models don’t predict CO2 emissions, which are an input to the models.

So they should run the models as they were when originally run for the IPCC in the First Assessment Report (FAR, 1990), in the Second (SAR, 1995), and the Third (TAR, 2001). Run them using actual emissions as inputs and with no changes of the algorithms, baselines, etc. How accurately will the models’ output match the actual global average surface temperatures? This was proposed by Roger Pielke Jr (Prof Environmental Studies, U CO-Boulder) in “Climate predictions and observations“, Nature Geoscience, April 2008.

Of course, the results would not be a simple pass/fail. Such a test would provide the basis for more sophisticated tests. Judith Curry (Prof Atmospheric Science, GA Inst Tech) explains here:

“Comparing the model temperature anomalies with observed temperature anomalies, particularly over relatively short periods, is complicated by the acknowledgement that climate models do not simulate the timing of ENSO and other modes of natural internal variability; further the underlying trends might be different. Hence, it is difficult to make an objective choice for matching up the observations and model simulations. Different strategies have been tried… matching the models and observations in different ways can give different spins on the comparison.”

On the other hand, we now have respectably long histories since publication of the early IPCC reports: 25, 20, and 15 years. These are not short periods, even for climate change. Models that cannot successfully predict over such periods require more trust than many people have when it comes to spending trillions of dollars — or even making drastic revisions to our economic system (as urged by Naomi Klein and Pope Francis).


Re-run the models. Post the results. More recent models presumably will do better, but firm knowledge about performance of the older models will give us useful information for the public policy debate. No matter what the results.

As the Romans might have said when faced with a problem like climate change: “Fiat scientia, ruat caelum.” (Let science be done though the heavens may fall.)

“In an age of spreading pseudoscience and anti-rationalism, it behooves those of us who
believe in the good of science and engineering to be above reproach whenever possible.“
P. J. Roach, Computing in Science and Engineering, Sept-Oct 2004 — Gated.

World Models

Other posts in this series

These posts sum up my 330 posts about climate change.

  1. How we broke the climate change debates. Lessons learned for the future.
  2. A new response to climate change that can help the GOP win in 2016.
  3. The big step climate scientists can make to restart the climate change debate – & win.

For More Information

(a)  Please like us on Facebook, follow us on Twitter, and post your comments — because we value your participation. For more information see The keys to understanding climate change and My posts about climate change. Also see these about models…

(b)  This is an obvious idea. I saw one mention of this on the web (e.g., by Carrick in this Sept 2013 thread at Climate Audit) — there are probably others — but nothing by a climate scientist — formally or informally made. We can only guess why.

The odds that no scientist thought of this are IMO zero. Why has this not been done? We can only guess.

(c)  I learned much, and got several of these quotes, from a 2014 presentations by Leonard A Smith (Prof of Statistics, LSE): the abridged version “The User Made Me Do It” and the full version “Distinguishing Uncertainty, Diversity and Insight“. Also see “Uncertainty in science and its role in climate policy“, Leonard A. Smith and Nicholas Stern, Phil Trans A, 31 October 2011.

(d)  Introductions to climate modeling

These provide an introduction to the subject, and a deeper review of this frontier in climate science.

Judith Curry (Prof Atmospheric Science, GA Inst Tech) reviews the literature about the uses and limitation of climate models…

  1. What can we learn from climate models?
  2. Philosophical reflections on climate model projections.
  3. Spinning the climate model – observation comparison — Part I.
  4. Spinning the climate model – observation comparison: Part II.

(d)  Selections from the large literature about validation of climate models

Despair: so common these days, so good for the 1%

Summary:  Despair at the confident predictions of doomsters has become an almost defining characteristic of both Left and Right in America, as documented in so many posts here. Nothing but abject servitude serves the 1% better.  Here’s an example, looking at the effects of the quarter-century-long campaign predicting doom from climate change.


Edvard Munch’s “Despair” (1894).

Assessing the record, and alarmists’ responses to it

Gore correctly predicted a “time of consequences”, but got the details backwards. He quoted Churchill’s 1936 warning about Hitler, given less than 3 years before the invasion of Poland. What have we seen 10 years after Gore’s speech, and 26 years after James Hansen’s Senate testimony)? Few of the predicted horrors have appeared.

The world is a fraction of a degree C warmer. The record pause in hurricane landfalls continues, global numbers and energy of hurricanes has not risen, number of severe tornadoes, area burned in wildfires, number of extremely hot days in the US, the extent of arctic sea ice, Antarctic sea ice, and area of global sea ice — most metrics of extreme weather have remained stable or within historical norms during the past decade (more details here and here). Nor is there evidence we’ve hit the “tipping point”, despite passing so many deadlines during the past 30 years.

Even the air temperature has frustrated Gore’s predictions, as the pause continues in its second decade while scientists debate its causes. The somewhat ramshackle global surface air temperature networks showed a peak of hundredths of a degree in 2014 (and YTD 2015), less than their error bars; the two satellite-based networks show no record for 2014 (details here).

The consequences: a loss of credibility for the climate change activists, as the US public rates it among the least serious threats (see polls by Pew Research and by Gallup). Historians might see this as one of the most incompetent publicity campaigns ever.

Instead of learning and adapting from their failure, climate activists have doubled down. They ratchet up their claims about future doom, with journalists’ support. Often contrary to the IPCC’s findings, as in these articles about the “methane monster”. And as in this gem…

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The Fed sees a darkening future – and the key fact about our economy

Summary: Today’s economic forecast by the Fed gives us another dose of bad news, wrongly overshadowed by their decision not to raise interest rates (resulting from it). Ignore economists’ guessing about the next tick up or down in the economy. The key insight is that America can’t grow fast but cannot afford to slow.  {2nd of 2 posts today.}

Fast Snail



  1. A darkening Fed forecast
  2. America in the “coffin corner”
  3. For More Information

(1)  A darkening Fed forecast

The Fed’s forecasts get too little attention, although they play a large role in the setting of Fed monetary policy. Since the crash the Fed has started its out-year forecasts high, and then dropped them at an accelerating rate as they approach the present. The high end of 2015 has fallen 40% vs. a fall of only 4% for 2017. Hope dies slowly.

  • 2015 from 3.0 – 3.8% in Sept 2012 to 2.0% – 2.3% now.
  • 2016 from 2.5 – 3.3% in Sept 2013 to 2.2% – 2.6% now.
  • 2017 from 2.3 – 2.5% in Sept 2014 to 2.0% – 2.4% now.
  • 2018 started at 1.8% – 2.2% (median of 2.0%).

As this graph shows, since the crash GDP has swung between 1% and 3%. When GDP falls below 2% the odds of a recession rise rapidly. This recovery already has had two close calls. The Fed responded to the slowdown that began in Q4 2010 with QE2 (Nov 2010), and to the slowing  that began in Q2 2012 with QE3 (Sept 2012).

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Will American remain a superpower? This graph has the answer.

Summary: Last week’s post looked at China’s rapidly slowing economy, bad news for the world economy. This post looks at the other half of the global power twins: America, and its long-term growth. Continued 2% growth in real GDP might keep us a superpower. Less than 1%, as eminent economist Robert Gordon expects, will not. The story is a bit technical, but important.  {1st of 2 posts today.}

“Our real problem, then, is not our strength today; it is rather the vital necessity of action today to ensure our strength tomorrow.”
Eisenhower’s State of the Union address on 9 January 1958.

The graph that will determine if the US remains a superpower

Forecast of US GDP Growth

Slower U.S. Growth in the Long- and Medium-Run

By Robert Gordon of National Bureau of Economic Research (NBER)
NBER Reporter, 2015 (1). Graphics and red emphasis added.

The annual growth rate of U.S. per-capita real GDP remained remarkably steady at 2.1% between 1890 and 2007. Until recently, it was widely assumed that the Great Recession of 2007-09 and the slow recovery since 2009 represented only a temporary departure from that steady long-run growth path. Growth theory, which tends to take the economy’s underlying rate of technological change as exogenous, was consistent with the widespread expectation that in the long run the economy’s growth rate would soon return to the longstanding 2% annual rate.

Federal Reserve Open Market Committee’s estimate of US long-term growth: 2.0 – 2.3%

In a series of research papers dating back 15 years, I have questioned the presumption of a constant pace of innovation and technological change. More recently, in several papers I have described a variety of “headwinds” that are in the process of slowing the economy’s growth rate independently of the contribution of innovation. Taken together, these headwinds and a slowing pace of innovation lead me to predict that the economy’s long-run rate of growth of per-capita real GDP over the next 25 years or so will be 0.9%, less than half of the historic pre-2007 rate of 2.1%.

And that 0.9% will not be available to most of the population, as growing inequality will cause a disproportionate share of available output growth to accrue to those whose incomes fall in the top 1% of the income distribution. Growth of per-capita real income for the bottom 99% of the income distribution will be 0.5% per year or less.

This research summary begins with a look at the factors involving innovation and the headwinds that are in the process of reducing long-run growth. A subsequent section describes a new technique to estimate the growth rate of the economy’s underlying potential output, an analysis which concludes that the economy’s potential growth rate falls well short of that currently assumed in the projections of the Congressional Budget Office (CBO).

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Are 30 thousand species going extinct every year?

Summary: The warnings become increasingly dire and shrill as we approach November’s United Nations Climate Change Conference in Paris. One theme warns about the increasing rate of extinctions, described with astonishing numbers — and projected to add humanity to the endangered species list. As usual, these claims distract attention from serious and imminent threats, such as our dying oceans. Let’s look beyond the hysteria to the science.

Extinction Poster



  1. Our certain doom from the great extinction.
  2. How many species are there?
  3. How many species have gone extinct?
  4. Should we fear forecasts of mass extinction?
  5. Conclusion.
  6. For More Information.
  7. For a useful perspective on these matters.


(1)  Our certain doom, chapter XXI: the great extinction

Exaggeration is the primary tool of activists in the publicity campaign to force public policy changes to fight climate change. “Anything goes” became their watchword once they broke free from the peer-reviewed literature.

It starts with science at the website Endangered Species International — “More than 16,000 species are threatened to become extinct in the near future.” “Of the 44,838 species assessed worldwide using the IUCN Red List criteria, 905 are extinct {was 784 in 2006} and 16,928 are listed as threatened to be extinct.”

Next politics goes wild: The Convention on Biological Diversity went into force in December 1993. Among its best known results are these words by Executive Secretary Ahmed Djoghlaf on 21 May 2007 — about extinctions happening now (not just threatened for the future).

“Every hour, three species disappear. Every day, up to 150 species are lost. Every year, between 18,000 and 55,000 species become extinct.  The cause: human activities. … Climate change is one of the major driving forces behind the unprecedented loss of biodiversity. “

This has frequently been debunked. But even after 8 years of rebuttals to this and similar exaggerations, Real News Network repeats this claim in Climate Change: Have We Reached the Point of No Return? (Climate change zombie myths live on the Left, much as Zombie Economics does on the Right.) The RNN story has the typical climate activists’ mix of unbalanced facts, assertions far outside the climate science consensus (and the IPCC), plus exaggerations. They used the poster at the top if this post as their headline graphic.

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The big question for the world: is China growing, slowing, or in recession?

Summary: China is both the key driver of the world economy and the least well known of the major nations. With unreliable economic statistics, a rapidly evolving economy that defies easy analysis, and deep corruption, it defies analysis. But its growth or recession might determine the course of the world economy during the next decade. This post provides a realistic outlook, debunking the dreamy consensus expecting continued rapid growth.

“God takes care that trees do not grow to the sky.”
— Ancient German proverb.

From Evercore: China might already be in a recession (red line)

Evencore: estimate of real China GGP

This graph is from a report by Evercore ISI), founded by Roger Altman (Asst Secretary of Treasury for Carter and Deputy Secretary for Clinton) — Excerpt…

“Our proprietary Synthetic Growth Index (SGI) fell 1.1% m/m in July, and was also down 1.1% y/y. No wonder global commodities are so weak. The most recent 18 months have been much weaker than the 2011-13 period. Even if we adjust our SG I upward (for too-little representation of Services — lack of data), we believe actual economic growth in China is far below the official 7.0% y/y. And, it is not improving, Most worrisome to us; the ‘equipment’ portion of Plant & Equipment spending is very weak, a bad sign for any company or country. Expect more monetary and fiscal steps to lift growth.”

A recession under way in China would explain the collapse of most industrial commodity prices (especially oil), and raise the risk of a global “recession” (usually defined as GDP growth slower than 2%). Fortunately, they are probably wrong about China’s current GDP. Such a fast slowing from 7% to -1% would create economics shocks impossible for even China’s government to hide. Like massive layoffs.

I believe their index shows the rising stress in China’s economy. See this anecdotal evidence in The Guardian: “China’s workers abandon the city as Beijing faces an economic storm. Labour disputes are rising and some workers are leaving for the country amid fears a crashing economy could cause political and social unrest.” However, I believe their underlying story is almost certainly correct: most estimates of China’s future growth are delusionally optimistic.

A recent paper by two eminent Harvard economists provides a more realistic forecast of much slower growth — which implies real recessions (falling GDP) for China, instead of just growth slowdowns. This is also likely for India. That would remove the steady wind that has helped power the world economy since 1990, with no obvious candidates to replace them as economic locomotives.

The top line in the below graph shows the common forecast that China will rule the 21st century, as its 6% or 7% GDP growth makes them number one. US GDP is almost $17 trillion, and growing at 2 – 3%, so China will equal us in roughly 10 years — if they can sustain such a high rate of growth. A transition to a slower rate of growth would change the world; doing so (as often happens) by a recession would rock the world.

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Ten years after Katrina: let’s learn from those predictions of more & bigger hurricanes

Summary — Most 10-year anniversary articles about Katrina omit one chapter of that sad story: its exploitation by climate activists. They predicted more and stronger hurricanes. Let’s grade them. Every time activists falsely cry “wolf” we become weaker, less able to prepare for real threats. Remembering is the first step to learning.

“Sooner or later, everyone sits down to a banquet of consequences.”
— Attributed to Robert Louis Stevenson.

Eye of the hurricane


  1. Katrina and Wilma hit America.
  2. Alarmists exploit the disaster.
  3. Hurricanes go MIA.
  4. Forecasts of  hurricanes.
  5. Conclusions.
  6. For More Information.
  7. A book recommendation.

(1) Katrina and Wilma hit America

The 2005 hurricane season was the most active on record by many measures. Ten years ago today Hurricane Katrina almost destroyed New Orleans (details here). Hurricane Wilma hit in Florida on 24 October 2005 (among the most powerful ever recorded in the Atlantic basin).

(2)  Alarmists exploit the catastrophe

Climate alarmists exploited this disaster. For example see Al Gore’s speech at Sierra Club’s National Environmental Convention and Expo in San Francisco on 9 September 2005 — excerpt…

“Winston Churchill, when the storm was gathering on continental Europe, provided warnings of what was at stake. And he said this about the government then in power in England — which wasn’t sure that the threat was real — he said, “They go on in strange paradox, decided only to be undecided, resolved to be irresolute, adamant for drift, solid for fluidity, all powerful to be impotent.” He continued, “The era of procrastination, of half measures, of soothing and baffling expedience of delays, is coming to a close. In its place we are entering a period of consequences.”

“Ladies and gentlemen, the warnings about global warming have been extremely clear for a long time. We are facing a global climate crisis. It is deepening. We are entering a period of consequences.

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