This is not a new topic for this section of PriusChat. But I bring to your attention an editorial in the journal "Weather, Climate, and Society" just plug in the digital object identifier doi:10.1175/WCAS-D-14-00005.1 It's free to download. the authors caution (quite reasonably) that extreme events always have and always will take place. We need to prepare for them in advance, which will often cost less than mopping up after. Entangling the concept with climate change per se will probably just bog down the discussion. Worse, some slowing of CO2 increase could lead to a false sense of security that 'now we are done with extreme events'. All good advice it seems to me. All quite in line with (the best of) Pielke's thinking (the younger one), which I have praised here before.
The co2 levels are all that is talked about concerning global warming here, global warming there. What folks don't talk about concerning global warming is much greater the co2: Water vapor. DBCassidy
Atmospheric water vapor plays a major role in the 'greenhouse effect' that keeps the Earth's surface much warmer than the moon's. For it to contribute to additional warming, it would need to increase. We've discussed here before that water vapor may be increasing slowly, but it is a difficult measurement. Briefly, you are looking for a small change in a large value, and that value varies widely across regions. For it to increase substantially, increased surface evaporation would have to go unbalanced by increased rain or snowfall somewhere. Could happen, does not seem to be happening yet. As climate/CO2 sensitivity is supposed to be amplified by water vapor increases, maybe it won't be (so much). So, maybe the lower CO2 sensitivity estimates are more reasonable. We are likely to know that very well with a few more decades of T measurements, even if the climate models don't improve enough to make the call. Meanwhile, I will take issue with the notion that folks don't talk about this. They do: Ancient Indonesian climate shift linked to glacial cycle -- ScienceDaily And it's not just talk. Serious sediment coring and isotope and geochemical work. Water vapor, at least, matters a lot for glacial / interglacial cycles.
For what it's worth, near-surface absolute humidity has increased since the 1970s, but the moistening over land has abated during "recent years", according to IPCC AR5 Final Draft Report (Chapter 2: Observations: Atmosphere and Surface - Final Draft Underlying Scientific-Technical Assessment, Page 2-50)
Wxman, I understand that radiosondes have used a variety of RH sensors over the years. That variation among individuals and intercalibrations associated with hardware changes have compromised detection of long term patterns. Have you experience in this area?
That's my understanding, but I worked at only one NWS office that was an upper air site (Brownsville, TX) in the mid-late 1990s. I know at that time there had been some changes to many of the radiosonde instruments, including the RH sensor, IIRC. Not sure what has been done since then. At any rate, thank you for the reference in your initial post. That more or less mirrors my view - expecting "extreme wx" to just end even with hypothetically returning atmospheric CO2 concentrations back to pre-industrial times is not realistic, IMHO.
I used Vaisala capacitive humidity sensors on tower-based installations. Take any 'N' of them and you will obtain a like number of different readings, including one that is quite different. This is not a knock on the manufacturer. If you want a reliable time series, be prepared to put in some effort. The original intent of radiosonde sampling was never to create long time series, so I am prepared to forgive them. Meanwhile while careful chartmanship can show that extreme events seem not to be increasing, that will only comfort a few who might be bringing an agenda to the table. Instead I go with the first-linked authors who essentially state that it is cheaper to prepare than repair. Clever, that. Too bad The Hindu newspaper penned it first in 2006.
I agree, expect AR5 Final Draft also concludes that there's no clear trend in most forms of "extreme wx" (so far at least). This is my summary interpretation of Chapter 2 ("Observations: Atmosphere and Surface")... Apparent Trends... Average Global Temps Warming (but "hiatus" since 1998) Temp Extremes (more "heat waves"; less "cold waves") Decreasing Snowfall in NH Mid-latitudes Surface & Tropospheric Absolute Humidity (increase has abated in recent years; RH decreasing) No Apparent Trends... Large Scale Changes in Precipitation (Spatial and intensity increase in some regions (NH mid-latitudes)) Streamflow and Runoff Cloud Cover Floods Droughts (except in certain regions which offset on global scale) Severe Local Wx Events Tropical Storms Extratropical Storms Surface Winds Upper Air Winds Upper Air Flow Configuration and Blocking (except poleward shift in jet stream) Changes in Climate Variability Any additions or corrections?
There have certainly been significant regional changes in precip and streamflow. With some areas getting wetter and others getting drier, the net global effect is not different from zero. But regional hydrology is what matters I suppose.
A Bell ("Gaussian") Curve -- extremes at either ends with a mean center value...given enough random data samples.
