NOAA: Hottest April and hottest Jan-April on record

Masters: Record Atlantic sea surface temps in hurricane development region, “The three past seasons with record warm April SST anomalies all had abnormally high numbers of intense hurricanes”

Temperature Anomalies April 2010.

NOAA’s National Climatic Data Center has published its monthly “State of the Climate Report.”  It pretty much matches the NASA data.

An emeritus physics professor writes me cautioning against the use of the word ‘anomaly’ since, “In many people’s mind, the word ‘anomaly’ means something unusual that is a temporary phenomenon.”  He suggests “change,” which is probably better.

Certainly for those who are communicating to the general public, like NOAA and NASA, ‘anomaly’ is a confusing word as used in these charts.  And that is especially true because the recent temperature trend is anything but an anomaly — it is in fact a prediction of basic climate science.

Indeed, besides the record April and record Jan-April, NOAA itself explain:

This was also the 34th consecutive April with global land and ocean temperatures above the 20th century average.

So, yes, that isn’t really an anomaly any more — unless of course you are in the anti-science crowd, in which case the whole thing is one big mysterious deviation from the norm.

As for the oceans, NOAA points out:

The worldwide ocean surface temperature was 0.57°C (1.03°F) above the 20th century average of 16.0°C (60.9°F) and the warmest April on record. The warmth was most pronounced in the equatorial portions of the major oceans, especially the Atlantic.

Meteorologist Jeff Masters discusses the implications in his WunderBlog:

Sea Surface Temperatures (SSTs) in the Atlantic’s Main Development Region for hurricanes had their warmest April on record….  The area between 10°N and 20°N, between the coast of Africa and Central America (20°W – 80°W), is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms.

When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Ni±o event present.) SSTs in the Main Development Region (10°N to 20°N and 20°W to 85°W) were an eye-opening 1.46°C above average during April. This is the third straight record warm month, and the warmest anomaly measured for any month–by a remarkable 0.2°C. The previous record warmest anomalies for the Atlantic MDR were set in June 2005 and March 2010, at 1.26°C.

As of now, the El Ni±o has in fact faded and that trend is projected to continue.

Figure. The departure of sea surface temperature (SST) from average for May 13, 2010. Image credit: NOAA/NESDIS.

What is the cause of the high SSTs in the MDR?

During December – February, we had the most negative AO/NAO since records began in 1950, and this caused trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region to slow to 1 – 2 m/s (2.2 – 4.5 mph) below average. Slower trade winds mean less mixing of the surface waters with cooler waters down deep, plus less evaporational cooling of the surface water. As a result, the ocean heated up significantly, relative to normal, over the winter. Negative AO/NAO conditions have been dominant much of this spring as well, resulting in further anomalous heating of the MDR waters.

This heating is superimposed on the very warm global SSTs we’ve been seeing over the past few decades due to global warming. Global and Northern Hemisphere SSTs were the 2nd warmest on record this past December, January, and February, the warmest on record in March, and will likely be classified as the warmest or second warmest on record for April, since NASA just classified April as the warmest April on record for the globe. We are also in the warm phase of a decades-long natural oscillation in Atlantic ocean temperatures called the Atlantic Multi-decadal Oscillation (AMO). This warm phase began in 1995, and has been partially responsible for the high levels of hurricane activity we’ve seen since 1995.

What does this mean for the 2010 hurricane season?

The high April SST anomaly does not bode well for the coming hurricane season. The three past seasons with record warm April SST anomalies all had abnormally high numbers of intense hurricanes. Past hurricane seasons that had high March SST anomalies include 1969 (0.90°C anomaly), 2005 (1.19°C anomaly), and 1958 (0.97°C anomaly). These three years had 5, 7, and 5 intense hurricanes, respectively. Just two intense hurricanes occur in an average year. The total averaged activity for the three seasons was 15 named storms, 11 hurricanes, and 6 intense hurricanes (an average hurricane season has 10, 6, and 2.) Both 1958 and 2005 saw neutral El Ni±o conditions, while 1969 had a weak El Ni±o.

The SSTs are already as warm as we normally see in July between Africa and the Caribbean, and we have a very July-like tropical wave approaching the Lesser Antilles Islands this weekend. However, wind shear is still seasonably high, and the tropical waves coming off of Africa are still too far south to have much of a chance of developing. The GFS model is indicating that shear will start to drop over the Caribbean the last week of May, so we may have to be on the watch for tropical storms forming in the Caribbean then.

The anti-science crowd have been cheering the death of El Ni±o, but in fact it it quite bad news for those in hurricane alley, including the long-suffering Gulf Coast.


24 Responses to NOAA: Hottest April and hottest Jan-April on record

  1. Hilda Orepesa says:

    Only 50 years of records? Only 30 years GISS?

    An honest and smart scientist would say that is not enough data to draw a conclusion.

    [JR: Huh? The GISS records go back over a century, which you’d know if you’d bother to look at the post on the subject. Post your disinformation elsewhere.]

  2. “An honest and smart scientist would say that is not enough data to draw a conclusion.”

    An honest scientist would already realize that GISS records are but a blip in the big scheme of climate science.

  3. Mark S says:

    I’ve got a el nino question for the CP crowd. Since ocean temps are up about .5 c during the 20th century, shouldn’t that qualify for a year round el nino? How do they calculate the baseline for el nino if the oceans have warmed that much?

  4. MAGB says:

    “Hottest April and hottest Jan-April on record”

    So why was Antarctica covered in forest 40 million years ago? What forces caused it to freeze? How are those factors affecting the climate now?

  5. GFW says:

    I’ve wondered the same thing Mark. If they don’t shift the baseline, we can still have variation in the equatorial Pacific large enough to shift between El Nino and La Nina, but over time, a mild El Nino state would become the average. It seems to me they *have* to shift the baseline. I could well be missing something though.

    On the hurricanes, my understanding is that there is a lot of high altitude wind-shear that is likely to disrupt hurricane formation at least in the first half of the season. I don’t know if there is a good prediction of the wind shear beyond that. One irony is that hurricanes stir up the ocean, cooling the surface, so hurricanes suppressed likely lead to stronger hurricanes later.

  6. MarkB says:


    I recommend the following presentation by Dr. Richard Alley…

    and a quick look at the geological history of Antarctica:

  7. GFW says:

    Because 40 Million years ago, the atmospheric CO2 was still likely around 800ppm, having fallen from considerably higher levels that kept the planet hot during the age of the dinosaurs. See

    Continuing decline in CO2 lead to the glaciation of Antarctica and the relatively recent set of glacial/interglacial periods.

    For an interesting, and very plausible explanation (supported by sediment cores) for how the high Jurassic levels of CO2 dropped, search for “Azolla Event”.

  8. Lore says:


    “So why was Antarctica covered in forest 40 million years ago? What forces caused it to freeze? How are those factors affecting the climate now?”

    This is a pretty basic question that has been answered in ad nauseam here and on most any other decent source for climate information.

    The simple answer is that all those known factors have been considered, which has led to the evidence pointing towards increased GHG emissions as the very likely suspect.

    Of course the blip in the big scheme matters when we are the ones in the middle of it.

  9. Rabid Doomsayer says:

    Antarctica might have been idyllic tens of millions of years ago, but how habitable was the rest of the planet? We may find out.

  10. Leif says:

    Anomaly = new normal.

    Antarctic still had 3 months of 24 hour dark and 3 months of 24 hour light millions of years ago.

    I do not feel it is fair to shift the base line for El Nino as the warming is added energy whether it is from El Nino or global warming. In essence the added green house warming would just make the El Nino that much more intense as the base energy must be dissipated no matter what. I would say that at some point we would get permeant El Nino conditions with a normal year from time to time. Recall that El Nino does not just effect the weather but the fish availability as well. If memory serves me correct El Nino years were a time of hunger in some areas of South America.

  11. Jim Eager says:

    MAG asks @4: “What forces caused [Antarctica] to freeze?”

    A steady decrease in atmospheric CO2, which started around 50 million years ago when the Indian subcontinent collided with Asia, forcing the uplift of the Himalaya mountain range and Tibetan plateau. That uplift exposed massive quantities of silicate rocks to natural weathering, which permanently removes CO2 from the atmosphere, albeit very slowly. By around 34 million years ago enough CO2 had been removed to reduce atmospheric concentration from around 1100 ppmv down to around 450 ppmv, with a consequent amplifying feedback reduction in water vapour, thus lowering average global surface temperature sufficiently for a permanent ice cap to form in East Antarctica. That ice sheet in turn increased Earth’s abedo, causing more incoming sunlight to be reflacted back out to space, further lowering global surface temperature.

    For more see here:
    and here

  12. BB says:

    I don’t think you can change the El-Nino baseline. To do so would effectively ‘shift’ and ‘adjust’ the current temperature anomaly profile over time (whether you think it’s to your advantage or not).

    There’s already been enough accusation of that sort of chicanery. If there was a wrong, two of them don’t make it right.

    Now, to discover that El-Ninos and La-Ninas are peterbations above and below a natural (predictable like the tides) sinusoidal baseline (to me) would take all sorts of research and probably decades to establish. If that researched conclusion exists, I’d like to see it.

  13. Steve Bloom says:

    FYI the future “permanent El Nino” state is projected to differ in important ways from current El Ninos.

  14. Paul K2 says:

    Mark S says: May 17, 2010 at 7:42 pm
    I’ve got a el nino question for the CP crowd. Since ocean temps are up about .5 c during the 20th century, shouldn’t that qualify for a year round el nino?

    Take a look at the chart that was posted on the previous post talking about record atmospheric temperatures; and which explained that far more thermal energy ends up in the ocean than in the atmosphere. Due to deep cold water with high thermal capacity, the ocean will take hundreds of years to heat up, and will be a heat sink during that time. But the surface conditions will still swing during the ENSO cycle (El Nino Southern Oscillation) as warm water builds up in the Pacific, until heat loss to the atmosphere coupled with upwelling/downwelling cools the surface layer.

    Incidentally, the ocean is saving us the worst consequences of our actions in many ways; the ocean also is a major CO2 sink that along with the soils and other carbon sinks are absorbing about 45% of carbon released from fossil fuels and man caused deforestation (carbon released from fires used to clear land). So the ocean is helping keep the lid on GW in several ways.

    I would suggest you read some basic material on global warming; the parts the ocean plays in preventing our planet’s biosphere destruction are critical in delaying some of the worst impact of AGW.

  15. mike roddy says:

    We seem to have a few WUWT refugees today, and I sympathize. Even they must have started to feel weird about cheerleading Anthony’s new weather stations project.

  16. Steve Bloom says:

    Joe, I’m not sure how to get your attention on this since I tried and failed before (yes, I know you’re busy), but the recent consensus among hurricane scientists that TC frequency will not go up meaningfully as the climate continues to warm has been shattered. It turns out that the model studies failed to account for the cooling lower stratospshere, which we know from basic physics will enhance TC efficiency, in turn counteracting the increased windiness that had been postulated to be the main factor in keeping future frequency from increasing.

    The paper describing this is from (who else) Kerry Emanuel and was presented at the AMS conference last week. Its findings are bolstered by other results from Jim Elsner discussed in this post by Masters (no paper as yet, though). It turns out that stratospheric temperature variation has a significant effect on Atlantic TC frequency (and in particular on U.S. hurricane strikes)over the eleven-year solar cycle.

    The Emanuel paper conclusions (bolding added):

    Observations suggest that the lower tropical stratosphere has been cooling over the last few decades. While the NCAR/NCEP reanalysis captures this cooling over the Atlantic during hurricane season, GCMs largely fail to simulate it. The cooling, especially when coupled to increasing SSTs, results in a large reduction of outflow temperature, an important component of potential intensity. The potential intensity, in turn, not only governs the intensity of tropical cyclones, but is an important component in setting the frequency of storms, as suggested both by downscaling studies and contemporary genesis indices. Atlantic tropical cyclone activity downscaled from NCAR/NCEP reanalyses after 1980 show remarkably good agreement with observed tropical cyclone activity during that period, but when the same technique is applied to two AGCMs forced by observed SSTs and sea ice, the substantial increase in Atlantic tropical cyclone activity after 1990 is almost completely absent, even though the simulations agree well with the historical data before about 1965. Since all the simulations use very similar SSTs, this suggests that the upswing in Atlantic activity since about 1990 is largely owing to the cooling of the stratosphere, which the GCMs fail to simulate.

    Whatever the cause of the observed stratospheric cooling, the fact that climate models do not simulate it and that it is apparently an important influence on tropical cyclones together warrant lower confidence in recent projections of the response of tropical cyclones to global warming

    Of course we know very well what’s behind long-term lower stratospheric cooling (in combination with tropospheric warming), as it’s famously a fingerprint of increasing GHGs.

    Finally, the conclusion that the post-1990 increase in Atlantic TC activity now can be attributed substantially to AGW is rather striking given the nature of the post-2005 scientific and political debates. Is it worth a mention on Climate Progress?

  17. Leif says:

    Even though a permanent El Nino state is projected to be different I believe some similarities can be inferred at least for a few years. Warmer waters do in fact adversely affect the availability of anchovies which in turn means less larger fish. In fact a quick Google search reports starvation during El Nino years. Moving a base line will not make the fish return. Warmer waters are also associated with coral bleaching. Regular El Nino conditions will exasperate that response as well. Warmer waters have been associated with the newly formed “Dead Zone” off the Oregon/Washington coast as well. In my youth commercial and sports fishing were one of the main economic foundations of the coastal area. That is all but gone now. Moving the “base line” will not bring back the fish here either. In fact there has been speculation by the scientists that the local Dead Zone is becoming a permeant summer feature. Dead Zones are increasing by about 10% per year around the world. That gives a doubling time of 7.2 years for the math impaired. Jeremy Jackson is giving the oceans of the world 30 to 40 years before becoming a microbial mat. Moving the base line will not help that outcome. Bon appetite!

  18. Chris Dudley says:

    In astronomy, the word anomaly is often used to mean something unusual and unexplained though it also has other technical uses. In geophysics anomaly seems to be often interchangeable with difference from the mean or model, not unexpected, just a manner of reporting a measurement. In fact, repeated zero anomaly (difference) would be anomalous (strange) for most measurements of interest. I think that in common use, the bizarre aspect of the word anomaly is often taken as connotation if not denotation. I agree that picking another word or phrase for use in public communication might be better.

  19. Leif says:

    Dead Zones, a quick google search. In 2008 it was reported that there was ~400 dead zones totaling ~95,000 sq. miles. If that 10% per year increase mentioned above continues to hold true, every inch of ocean will become a dead zone in ~65 years. That is within the life time of my grand son. Continental shelves in ~30 years is very doable. I just have to make it to a hundred to see that.

    These are the facts Anti-Science folks.

  20. fj2 says:

    19. Lief, “Dead Zones”

    Yes, dead zones are an extremely important issue but somewhat off-topic and it is not clear the affect of violent storms which may be both beneficial and detrimental.

    Increased mixing of local oxygen along with cooling; increased mixing of CO2.

    Increased heating of land surfaces where high winds are dissipated.

    Hopefully there is a serious deadzone watch in the Gulf as this may be the most immediate and extremely dangerous characteristic of the accelerating environmental crisis.

    Difficult to quantify, the marine environment provides enormous resources as one of those rapidly deteriorating “known unknowns” perhaps the first major threat to civilization as we know it; though, unfortunately mass starvation is another on a global scale and not quite so local.

  21. MapleLeaf says:

    It is not only the oceans which are warming. New study from Nature Geoscience finds that water temperatures in Lake Tanganyika are the highest/unprecedented in the last 1500 years. No UHI there Mr. Watts, and Steve McIntyre the HS lives on:

    Steve Bloom #16, that is a fascinating find with significant implications. Dr. Emanuel is conducting incredibly important work.

  22. Paul K2 says:

    I second the comment from MapleLeaf; the Emanuel paper that Steve Bloom posted in comment #16 is a jaw dropper. And the thermodynamics behind it makes total sense. Please note that I am an engineer, not an atmospheric physics expert, but here is my interpretation of the paper:

    Emanuel shows that the stratosphere near the tropopause is cooling, an effect that is exacerbated by the GHG effect (cooling stratosphere is one of the key signatures of GHG effect), but in this paper the lower ozone concentrations in the lower stratosphere are identified as the biggest reason that the lower stratosphere has cooled.

    The lower temperature in the lower stratosphere is almost certainly leading to lower outflow temperatures from hurricanes (the temperature of air ‘packets’ leaving the hurricane circulation system. Emanuel shows this effect accounts for much of the increased energy output by tropical cyclones, as measured by Potential Intensity (PI). The other key factor that raises PI, is the sea surface temperatures (SST). Emanuel shows that increasing SST alone cannot explain the increase in Potential Intensity, but increased SST (as observed) plus lower outflow temperatures due to a cooler lower stratosphere, does seem to explain the large rise in PI over the last five decades.

    From a thermodynamic standpoint, this makes total sense. A Carnot cycle operates between a heat source and a heat sink, and the amount of power generated from the cycle increases when the heat source temperature increases, or when the heat sink temperature is lowered. As anyone who has done any low temperature power plant calculations can attest, a 5 K rise in temperature from the heat source is important, but a 5 K drop in heat sink temperature is even more significant in increasing the power output. These tropical cyclones are giant heat engines, and the lower outflow temperatures are going to cause bigger and stronger storms.

    Excellent paper, covering critical impacts of AGW and ozone layer depletion.

  23. Alex says:

    Heres the tricky thing about ENSO and the North Atlantic TC connection. The intermediate mechanism that has been proposed to explain this linkage is wind shear (see Gray’s classic 1968 paper), as outflow from ENSO anomalies in the Eastern Pacific increases shear aloft in the MDR and Western Atlantic. The teleconnection is also delayed by a couple of months (something that can be easily shown using NCEP reanalysis and HURDAT), and so even a subsiding El Nino in May can still suppress N. Atl TC activity well into the hurricane season. While the SST anomalies we are seeing are eye-popping, we should be looking at all the different environmental factors that go into the TC recipe.

  24. substanti8 says:

    I hear hurricanes a-blowin’
    I know the end is comin’ soon
    I fear rivers over flowin’
    I hear the voice of rage and ruin

    Don’t go around tonight
    Well, it’s bound to take your life
    There’s a bad moon on the rise

    Hope you got your things together
    Hope you are quite prepared to die
    Looks like we’re in for nasty weather
    One eye is taken for an eye

    Creedence Clearwater Revival
    (written about Hurricane Camille, 1969)