Also, African Rain Moves Westward?

UPDATED, 1/10/2007:
2006 was the warmest year on record, it was reported today, ahead of the previous title holder, 1998. 1998 was influenced heavily by the El Niño that began in 1997. And, sure enough, scientists have concluded that this year’s Niño was, effectively, super-charged by global warming. From the right-leaning Chicago Tribune:

In 1998, record high temperatures were driven by an unusually powerful El Nino current that disrupted weather patterns worldwide. The current El Nino, a periodic warming current that took shape last summer, is far weaker and has had only a moderate effect on global climate, several experts said.

“What we are seeing is much more than El Nino,” said climate analyst Kevin Trenberth at the National Center for Atmospheric Research in Boulder, Colo. “The overall pattern is consistent with our concepts of global warming.”

The original blog entry:
Part 1: El Niño 2006-07: Overachiever or Cheat?

As most people are aware, an El Niño formed in autumn of 2006 and has continued to this date. This event was basically single-handedly responsible for cutting off the 2006 hurricane season at the knees. El Niños do that — the last time we had one, it developed in late autumn of 2004 and ended a two-month streak of damaging hurricanes. And that one wasn’t even very strong. It was weak enough, in fact, that most articles in the popular press that talk about this year’s event don’t even refer to 2004; they say that the last El Niño was in 2002. The one this year is a moderate Niño.

This NOAA site shows the Oceanic Nino Index, an indicator of the temperature departure from the average for various three-month periods, going back to 1950. Positive values indicate El Niño-like conditions and negative values indicate La Niña. The site isn’t updated to reflect the new values, but they have increased past the levels of the 2004 Niño event.

The bottom line, though, is that this year’s event is not even close to the strength of the notorious 1997-1998 event. It is moderate. Mild.

Yet, during the most recent period of warmth for the Eastern United States, heat records were set in numerous eastern cities. The most common date for the old records?

Yep, 1997. There was a winter “heat wave” during the same time period during that year’s Niño as well.

The phenomenon causes warmer-than-usual winter temperatures for this half of the North American continent, but by all accounts, the 1997 records should not have been broken. This year’s event is not that strong.

What’s the lesson? I guess it is this. Global climate change apparently does not alter the effects of El Niño and La Niña — at least, as long as the oceanic conveyor belt current system remains intact. (If it were to collapse, as some predict, all bets are off.) It just intensifies El Niño events. It’s not just me saying this, either; the scientific consensus is moving in this direction. As for this year’s Niño, global warming appears to have super-charged it so that it produces effects similar to those of the significant 1997 event.

What else might it be affecting? I’m going out on a limb here, but I think I am onto something.

Part 2: The New Hurricane Paradigm

The Sahel area of West Africa used to be part of a multi-decadal wet/dry cycle. For two or three decades at a time, this area would receive significant rainfall; then it would switch to drought conditions. This cycle was linked as well to the ocean temperature of the Atlantic, to prevailing winds, and to Atlantic hurricane activity. As the African rainfall total increased, the ocean temperature would increase, the prevailing winds would become favorable for tropical development, and more hurricanes would form. The opposite relationship also occurred.

This was observed for as long as hurricanes have been tracked. And when researchers decided to retroactively track hurricanes from the past, they also obtained data on African rainfall for this period. They had developed predictive formulas that took the rainfall data as an input and spat out a hurricane forecast, and they fed the old rain data into them and compared the formulas’ totals against the observed numbers for these years. The relationship held up.

There is a group of scientists at Colorado State, formerly led by hurricane expert (and, ironically, global warming skeptic — a dying breed among scientists) Dr. Bill Gray, who has since then moved on. This group issues a series of predictions each year for the upcoming season, beginning in December of the preceding year. They issued their 2007 forecast, predicting that El Niño would break down and the season would be a bad one.

Okay. No big surprise. This past year was a bit of a fluke.

I read on. They mentioned the African rain-Atlantic hurricane connection, something I’d known about for several years now. They talked about how the statistical relationships that the research community had developed would normally figure prominently in their predictions, because they were so dependable. The statistical correlation was so strong.

Well, in 1995, it would seem that the relationship completely broke down.

Mind you, West Africa has been in a drought for decades. It’s a major part of why there are so many political upheavals and humanitarian disasters there. The drought began back in the late 1960s — at the end, incidentally, of the last active hurricane cycle.

The drought continued through the 70s, 80s, and early 90s, the statistical relationship holding. With a few exceptions, those were mild years for hurricanes. But in 1995, the ocean temperature shot up, the winds shifted, and the big hurricanes started coming again.

Africa remained in a drought.

In fact, Al Gore’s book and movie An Inconvenient Truth make special mention of the extreme drought conditions in Africa. There is a chart in the book and movie, a map of the world, that displays changes in average rainfall for land regions over the past several decades. Africa has dried up. Rather interestingly, the Gulf of Mexico and the Atlantic coast of Florida have had their rainfall totals skyrocket.

The chart doesn’t display rain data for the middle of the ocean, just land areas and areas very close to land. But I rather suspect that those weather patterns that used to form over Africa and contribute to hurricanes have shifted westward with the onset of global climate change. There’s really no other explanation for it. The moisture that fuels these things has to come from somewhere, and the other observed events in the multi-decadal cycle have occurred. The Atlantic has warmed up, and the wind patterns have shifted as would be expected. The rain has increased, too, just not where it used to.

Returning to Gore’s work, I think I can guess at what has happened. He mentions that global warming increases rainfall and warms up the oceans, but it also increases drought. Basically, higher temperatures in the atmosphere mean that more water vapor everywhere is being sucked up. I would hazard a guess that this would account for why Africa has remained in a drought while the hurricanes have returned; the water vapor that fuels them is coming from the ocean rather than from the African thunderstorms.

And, indeed, Hurricane Katrina exhibited this exact sequence. It began as Tropical Depression 10, a Cape Verde system (a tropical system originating off the coast of Africa). TD 10 dried up and fell apart as it moved over the ocean. It re-formed in the Bahamas as TD 12, then exploded into Katrina as it crossed Florida and hit the Gulf. That’s where the water vapor was.

If this is the start of a pattern, and I think it is, then it is not a good one. Africa needs that rain in the form of seasonal thunderstorms a lot more than the Coast needs it in the form of catastrophic hurricanes. But this, too, is what Gore’s work predicts: “More rain falls in big storm events” is almost a direct quote.

I have become hyper-aware of this issue in recent months. It is fast moving up my radar as the most important issue of all to me, and if it can pass election reform, outsourcing, and the war, that’s saying a lot. What I have read about is unsettling, and what’s been observed is frightening because it mirrors what has been predicted. I hope it’s not too late to do something about it. We elected this new Congress for a reason; I am more than ready for it to be addressed.