Terra Incognita: "unknown land." It's the phrase early mapmakers applied to land beyond the boundaries of the known world. Some conceptions were fanciful--the phrase "Here there be dragons" was sometimes used to express the perils of the unknown, or a mammoth waterfall to delineate the seas' furthest edge--but the words Terra Incognita were a simple and powerful reminder of the limits of knowledge.
Terra Incognita, to my mind, describes where we are today in terms of climate and weather. And in this part of Terra Incognita--central Vermont--it's raining.
The nearest weather station to our home reports that so far today, we've had 0.8 inches (20 mm) of rain. On Thursday, two days ago, the same station reported 1.27 inches (32 mm). And so it's gone, off and on, most of the year. We missed the peak rains of Tropical Storm Irene, but still got 4 inches (100 mm). And a few days later, the remains of Tropical Storm Lee arrived, and we got soaked again--2.76 inches (70 mm) spread over five days.
Earlier this year, the National Weather Service reported that Burlington recorded a record of 24.4 inches (620 mm) of rain from January through May. That total was more than four inches above the previous record (20.21 inches, 513 mm, in 1983) and more than 6.5 inches ahead of the third-place year (2000, with 17.74 inches, 451 mm). (Vermont's records, by the way, go back to 1850.)
It wasn't just Vermont, either. For March through May, the National Climatic Data Center found that Vermont, New York, Pennsylvania, West Virginia, Ohio, Indiana and Kentucky, Colorado and Washington all had their wettest springs in 117 years. Michigan, Montana, and Oregon had their second wettest. And Binghamton, NY, deserves special mention. On September 8 (remains of TS Lee), Binghamton broke its all-time 24-hour precipitation record--by more than 60%!--with 7.49 inches (190 mm).
What's the connection between heavy rainfall and global warming? Evaporation. As ocean waters warm, more water evaporates, and warm air can hold more moisture. That simple fact, plus a small amount of warming, has meant unprecedented rain events in many parts of the world. Besides Binghamton, Pakistan--where truly biblical flooding has happened the past two summers--comes to mind, along with Tennessee, Queensland and more.
So that's the rainy part of Terra Incognita. What about the other parts? Perhaps now would be a good time to say that by Terra Incognita, I don't mean truly unknown. As climate change deniers tirelessly remind us, every weather extreme that is now occurring has happened sometime in the past. But what we are seeing now is still "incognita" in the sense that it hasn't been experienced by anyone now living in the area involved--we're moving into weather none of us have known, and it's not just occurring in Siberia or the Hindu Kush or some other unthinkably remote place, it's happening right in our own backyards.
There's the Terra Incognita of drought and heat--in July, Oklahoma recorded the hottest month ever, not just for Oklahoma, but for any state in the U.S. Texas's drought has been even further off the charts--the Texas State Climatologist, John Nielsen-Gammon, commented, " ... [W]ith no previous points so dry it’s hard to say exactly what history would say about a summer such as this one. Except that this summer is way beyond the previous envelope of summer temperature and precipitation." NASA's James Hansen, who told Congress in 1988 that signs of global warming were becoming apparent and that we are "loading the climate dice" in the direction of more extreme weather, now says that parts of the southern U.S. may become "almost uninhabitable" in the not too distant future.
And there's the Terra Incognita of ice. It's melting. For some eye-popping numbers, check the first graphic in this post on Arctic sea ice. It shows that estimated sea ice volume in the summer of 2011 was less than 1/4 what it was in 1979, 32 years ago, and less than half what it was as recently as 2006. !
The melting of Arctic sea ice carries some further potential negative implications--feedback from open water absorbing more of the sun's heat than reflective ice, feedback from release of methane locked up in permafrost, and the simple release of more heat energy that is currently going into melting cubic kilometers of ice. But I'll leave those for another time.
Right now, it's morning, and the forecast here for today is: rain. As we collectively sail out into open waters and slowly watch the known land disappear, I'm hoping there isn't a giant waterfall somewhere ahead beyond the horizon. I'm sure that faint roaring sound I hear is just my imagination.
UPDATE - 9 October 2011 - Here's a report by Weather Underground's Dr. Jeff Masters from the Terra Incognita of ozone: a large and unexpected ozone hole opened in the Arctic this spring, and it's reasonable to think that it is linked to climate change. Why should we care? "The total loss of ozone in a
column from the surface to the top of the atmosphere reached 40% during
the peak of this year's Arctic ozone hole. Since each 1% drop in ozone
levels results in about 1% more UV-B reaching Earth's surface (WMO,
2002), UV-B levels reaching the surface likely increased by 40% at the
height of this year's hole. We know that an 11% increase in UV-B light
can cause a 24% decrease in winter wheat yield (Zheng et al., 2003), so this year's Arctic ozone hole may have caused noticeable reductions in Europe's winter wheat crop." (emphasis mine)
UPDATE - 29 October 2011 - More from Climate Progress on the Terra Incognita of Rain: extraordinary flooding in El Salvador follows similar deluge in Thailand. We are seeing the consequences of a modest increase in evaporation--in spades.