29 December 2009

The Earthquake vs. Weather Trick

It has become common of late to observe that the number of weather-related disasters has increased faster than the number of earthquake-related disasters, and imply directly or indirectly that the different must be due to greenhouse gas induced climate changes. The image above comes from UNEP. Or consider this excerpt from a news article out today quoting Munich Re:
Munich Re AG, one of the world's largest reinsurers, Tuesday said economic and insured losses caused by climate change will continue to grow, and called for a near-term deal to ensure a substantial reduction in global greenhouse-gas emissions.

"We need as soon as possible an agreement that significantly reduces greenhouse gas emissions because the climate reacts slowly and what we fail to do now will have a bearing for decades to come," said management board member Torsten Jeworrek.

"In the light of these facts, it is very disappointing that no breakthrough was achieved at the Copenhagen climate summit in December 2009," Mr. Jeworrek said, pointing to the marked increase--more or less tripling--in major global weather-related natural disasters since 1950. . .

"In particular, the trend toward an increase in weather-related catastrophes continues, while there has fundamentally been no change in the risk of geophysical events such as earthquakes," said Peter Hoeppe, who heads Munich Re's Geo Risks Research unit.
The problem with such statements is that everywhere that scholars have looked with respect to weather related disasters no greenhouse gas signal has been seen, including in the peer reviewed work published by Munich Re (e.g., here and here). If a signal of GHG-driven disasters can't be seen in the weather-related events alone, then adding a comparison to earthquakes won't add much to the analysis.

What then might be going on then to explain the disparity in earthquake and weather-related events? The answer should be obvious.

The data in the graph above above are compiled by CRED in Belgium with the assistance of Munich Re. Here are the criteria for an event to be included in the dataset:

For a disaster to be entered into the database at least one of the following criteria must be fulfilled:

• Ten (10) or more people reported killed.
• Hundred (100) or more people reported affected.
• Declaration of a state of emergency.
• Call for international assistance.
Obviously any trends in reporting of events over a long time period will effect the aggregate totals.

My hypothesis is that since 1980, which is the time period for which claims are most often made regarding the weather-earthquake divergence, very few large earthquakes are missed in the CRED database, because earthquakes are relatively rare and their effects are widespread. By contrast weather events, such as floods, are very common and can have very localized impacts that might not be reported or easily added to the CRED database. So the difference between earthquake and weather disasters reflects a relative increase in the report of small sized weather events I have emailed CRED to ask for comprehensive data that will allow me to explore this hypothesis more systematically.

Meantime, I performed the following test. I picked a random region in the CRED EM-DAT database and searched for all flood events in West Africa (Benin; Burkina Faso; Cape Verde Is; Cote d'Ivoire; Gambia The; Ghana; Guinea; Guinea Bissau; Liberia; Mali; Mauritania; Niger; Nigeria; Senegal; Sierra Leone; St Helena; Togo) in the 1980s, 1990s and 2000s. Here is what that data look like:

One response to this graphic might be to conclude that an increase in GHG-driven floods are responsible for the 3-fold increase in flood disasters with 10 to 60 people in Western Africa. Another would be to note the obvious -- only 5 events in a decade with a loss of 10 to 60 people is certainly an underestimate in a region with 300 million people, many who are very vulnerable to disasters, subject to frequent flooding and where reporting is probably not very systematic. In fact, the events in the 1990s and 2000s are also probably underestimated by some significant but unknown degree. In any case, to use such data to say anything about human influences on climate is unwise.

The bottom line here is that if you want to look for a signal of GHG-driven climate change, look at quality data systematically collected in particular regions for specific phenomena. If you cannot see a signal in that data, then going to less precise and more aggregated data will not add much value. A comparison of trends in weather and earthquake disasters sheds no light on the attribution of disasters to GHG emissions.


  1. Roger,

    Do you think these folks have made a conscious decision to make this tradeoff? People with the intelligence to exercise a little logic are obviously going to see through this silliness. Surely they have to know this. Thus, it appears that their desire to influence foolish people to support climate politics is trumping their concern that increasing numbers of intelligent people will consider them a laughingstock.

    The fact of the tradeoff is clear. My question is whether you think they explicitly recognized the trade and decided to do it anyway.

  2. World population growth a great match to the diaster curve http://en.wikipedia.org/wiki/File:World-Population-1800-2100.png . This is a true hockey stick:)

  3. I think the 'industrial accident' death toll for west africa is somewhat more revealing then the death toll from floods possibly caused by CO2 emitted by the developed world.

    On another note...how are Tsunami's counted..the death toll tends to be from flooding, but an earthquake is the precipitating event.

  4. It would be interesting to compare the G7 to the rest of the world.

  5. Worldwide seismograph networks identify the location and approximate size of every significant earthquake worldwide within a matter of minutes. It's virtually impossible for a significant earthquake to go unreported, and has been for several decades dating back to nuclear test ban treaty verification in the 1960's.

  6. Why didn't you mention your own hurricane landfall study?

  7. -6-Joel

    Not only are there no trends in US hurricane losses once normalized, there are no trends in tropical cyclone landfalls anywhere in the world.

    So the cyclone curve must be due to reporting.

  8. The post 1980 trend lines fit with the size of the ozone hole reasonably well.

    I would agree however that it's apples and oranges. Changes in land use and population in addition to improved reporting all have an impact.

  9. Well weve seen sunspecks become sunspots, weather depressions become storms, bushfires become fire storms etc - most of it is simply in the definition and by simply changing the definition the alarmists can lay claim to 'proof'!

  10. Interesting snippet here


  11. It is evident that a large proportion of minor flood events are underrepresented (missing) in the records over the 80s and somewhat in the 90s. This is the origin of the alarming trend detected in the 2000s.

    The big question here is what is going-on with earthquakes. Why are they apparently well represented over the 80s, 90s and 2000s. So far there is not a convincing answer to this.

  12. Roger, I think reporting is not even the problem. There is a more important mechanism at work. People are always assuming that exposure and vulnerability to weather and non-weather disasters develops exactly the same. Some studies (below) actually shows that they diverge. Now would that not make a more logic reason for the divergence in number and cost of disasters?


  13. -12-Laurens

    Thanks, there are obviously other factors at play, but I'd argue that the reporting issue is particularly acute with respect to the CRED dataset used by UNEP.


    See -5- above. I don't think that there is much mystery here.

  14. Yes, I would agree that reporting is an issue too, but at least this is acknowledged by oranisations, such as Munich Re, that mostly report on large and well covered events since 1970s/1980s. Seems that UNEP indeed is a bit less careful.

  15. Instead of earthquakes I would be interested in correlation to the hour of the day and whether it was daylight or dark.

  16. The gross correlation is meaningless.

    The street I live on has been prone to minor flooding for a decade.

    It can be a result of
    A) Global Warming
    B) A change in zoning of going from an R-1 zoning(1 residential home per acre) with a 20% impervious surface limit to R-6(6 homes per acre) with a 70% impervious surface limit.
    C) Both

    When the latest round of surrounding McMansions went up...the flooding on our little street ended up being 330 days a year. Regardless whether or not it had rained recently.

    So the fundamental problem of labeling 'climate' related is that the scope and scale of climate related disasters is defined by land use.

    This is one of the reasons AGW is losing it's credibility.

    Too many people can see for themselves that 'Disasters' being blamed on AGW are actually poor or il-advised land use policies. (Building houses behind a 100 year levy in Hurrican Ally is probably another poor land use policy

  17. Not one of the criteria used to make the claim that CO2 is causing more weather related disasters actually shows that CO2 is responsible for anything at all.
    What an utterly vapid excuse for a study.

  18. You see the same relationship on floods for Western Europe. You also mislabeled the graph, although you did put the correct criteria in the text.

  19. Hi !
    it's strange, the HAARP project has been created in 1993 and just after, there's an amazing increasing of disasters...
    (I found your article by searching the number of disasters per year to compare to the H.A.A.R.P creation date... because I had a doubt... it seems I was right ! )

  20. I think this affair is so concerning just as Generic Viagra
    is too. I mean, I hope everything goes fine for everyone