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Selected Resources for World Water Day

World Water Day 2010
More than one billion people (1 in 6) do not have access to adequate clean fresh water – which is defined as just 20 to 50 liters per day. (In contrast, the average American can use in excess of 400 liters per day indoors.) More than 2.5 billion people do not have access to basic sanitation facilities. Without sanitation, human and animal wastes reach drinking water supplies and illness proliferate. Diarrhea, caused by water-born pathogens, is the leading cause of illness and death in the world. And most of its victims are children under 5 years old.

Today is World Water Day, an annual recognition of the importance of freshwater and an opportunity for focusing attention on advocating for its sustainable management. World Water Day is organized by the UN Environmental Program. Each year has a particular theme, and in 2010 the theme is “Clean Water for a Healthy World.”


The all-around excellent Pulitzer Gateway “Downstream”is focused on water conflict and cooperation, water and economics, water and health, and water and climate. Of particular relevance for this World Water Day is the section on water and health, where I found the video and written account of women in Kakuma daily digging a dry riverbed for water because they couldn’t afford the 5 cents per jerry can fee for the clean, pumped water supplied by aid organizations and the local government.

(One thing you might notice if you watch some of these videos is that it is women and girls who are disproportionately affected by lack of access to clean water. Women are the ones who have to walk miles to fill jugs with water and girls drop out of school in order to do so. Improving access to water would give these women and girls additional opportunities to contribute to their own and their families’ economic well-being.)

In 2000, the UN set out its Millenium Development Goals, one of which is “By 2015, reduce by half the proportion of people without sustainable access to safe drinking water.” With five years to go, we haven’t gotten very far towards that goal. There are many organizations working to install wells and establish clean water supplies. There are also organizations working to develop and distribute affordable water purification technologies, some even using entrepreneurial solutions. Just as importantly, there are groups working to improve sanitation conditions. We need to break the taboo on sanitation and recognize it to be a necessary ingredient to preserving clean water resources. Unfortunately, all of these well-meaning organizations face significant limitations because of cost, political instability, hydrogeology, and climate.

No matter how much scientific geek-love I may have for streams and groundwater, mostly I take water for granted. Yet in other parts of the world, access to clean water is literally a matter of life or death. I’m glad for this year’s reminder of how fortunate I am, how far the world needs to go to meet basic human needs, and how many of the solutions are within our grasp, if concerted, adequately-funded efforts were made. Simply put, global health depends on access to adequate clean water and sanitation. It’s time to move water higher on our collective to-do list.

Here comes the Sun

This post cross-posted at Highly Allochthonous.

The Earth’s axis has a 23.44o obliquity or tilt to it. As the Earth revolves around the Sun over the course of a year, the axial tilt means that different parts of the Earth’s surface receive direct sunlight at different times of the year. And it’s this receipt of varying intensities of solar radiation that drives temperature differences, and hence seasonality.

Today is a solstice, illustrated by the image on the far right below. Today is the day of the year when the Northern Hemisphere is tilted farthest away from the sun and the Southern Hemisphere is tilted most towards the sun. For those of us in the Northern Hemisphere, it’s our shortest day of the year and the sun never gets very high in the sky, even at noon. In fact, the word solstice has a Latin origin in the word solstitium, where “sol” means sun and “stitium” means stoppage. and for several days around the solstice this noontime elevation appears to be the same – hence the stoppage. Today, the noontime sun appears directly overhead along the Tropic of Capricorn, 23.44o S.

305px-North_season.jpgFigure 1. Earth at the solstices and equinoxes, as seen from the north. Source: Wikimedia.

The precise moment of the solstice occurs at 17:47 UTC (12:47 pm Eastern Standard Time). We’ll have another solstice (image on far left) on 21 June 2010 at 11:28 UTC ( 7:28 am Eastern Daylight Time). Over the course of the Earth’s trip around the Sun there will be two moments when everybody is getting their fair share of sunlight – the equinoxes. In 2010, they’ll occur on 20 March 2010 at 17:32 UTC and 23 September 3:09 UTC (22 September 11:09 pm EDT).

Earth’s tilt also varies over geologic time. It has a ~41-thousand year cycle, and right now we’re at about the middle of the range in variation of axial tilt. As tilt increases, seasonal contrasts over much of the world increase, but it is decreased axial tilt is tied with the onset of continental glaciation. That’s because at high latitudes, when tilt is low, summers are even cooler, and more snow persists through the summer. That surviving snow forms the nucleus of glacial ice caps. We’re currently on the decreasing limb of the obliquity cycle, but based on past occurrence of continental glaciations, the onset of another one is going to require not just less obliquity, but also the right eccentricty and precession in the Earth’s orbital parameters and controlling greenhouse gas emissions.

Figure 2: Last seen at Clastic Detritus in 2007, original created by Slumbering Lungfish.

A few semantics about climate variability and change

Last week, the Southeastern United States received several inches of snow. This late season snowfall was certainly a novelty, though not an unprecedented occurrence. But it did stir up conversations among local residents, especially when the week ended with ~25 degree Celsius (75 Fahrenheit) sunshine. The weather’s fickleness also got me thinking about climate variability and climate change and how easily we can slip up and confuse the two. I even see scientists (who should know better) conflating variability and change, so below I offer a short, illustrated tutorial on the differences.

Hydrometeorological variables are things like precipitation, streamflow, groundwater levels, temperature, and humidity and are often expressed as annual or seasonal averages. The average value of one of those variables over 30 years is called a climatological normal. Below, I’ve illustrated a hypothetical climate variable as it varies of a 30 year period. These normals are redefined every 10 years, so right now we are using 1971-2000 as our normal period.

An example (hypothetical) climate variable through time

Figure 1. A hypothetical climate variable through time

The average value of the variable is 0.5, and the squiggles above and below the mean represent climate variability. I’ll define climate variability as the oscillations around a mean state. (An aside: it’s fairly common to see a few years in a row that are below the mean or above the mean, in a phenomenon known as serial correlation, where the value of a variable is influenced by the values that precede it. As an example, if you have a severe drought one year, even if it rains more than normal the next year, streamflow may stay quite low as groundwater is replenished. This is what is happening in the southeast now after our 2007 drought.)

Variability then is all about the oscillations, but it doesn’t tell you anything about what’s happening with the mean. Below, I’ve illustrated the same time series shifted progressively by 0.003 per time step. Here the mean is changing, while the variability stays the same.

A (hypothetical) climate variable in blue is trending by 0.003 per year (with the non-trending time series in gray for comparison)

Figure 2. A hypothetical climate variable in blue is trending by 0.003 per year (with the non-trending time series in gray for comparison)

As in the illustration above, variables like average temperature and sea surface temperature are experiencing changes in their mean values. So, climate change can take the form of a trend in the mean value of a variable over time. A climatological variable experiencing change in the mean would not have the same “normal” values from one climate normal period to the next.

But climate change can also affect the variability of a variable, as illustrated below. Here the mean is not changing, but I’ve made below-mean points successively lower by 0.0067 per time step and above mean points are successively higher by 0.00347 per time step.

A hypothetical climate variable (blue) showing an increase in variability with time (gray line is the variable with unchanging mean and variability)

Figure 3. A hypothetical climate variable (blue) showing an increase in variability with time (gray line is the variable with unchanging mean and variability)

This sort of change is the sort of change we might see in precipitation in some areas. For example, the Southeastern United States is predicted to have more intense summer rainfall and more intense droughts, and retrospective trend studies suggest that this may already be the case. Even though the mean precipitation is not changing, the Southeastern United States is still experiencing a climate change effect manifested in a change in climate variability.

Finally, climate change can take the form of a trend in the mean and a trend in the variability, as shown below.

A hypothetical climate variable with changing mean and variability (gray solid line indicates variable with unchanging mean and variability, gray dotted line has a changing mean without changing variability)

Figure 4. A hypothetical climate variable with changing mean and variability (gray solid line indicates variable with unchanging mean and variability, gray dotted line has a changing mean without changing variability)

This final pattern may be the case for streamflow in some regions. Mean streamflow could decrease because of increasing evapotranspirative losses in a warmer climate, and streamflow variability could increase because of changes in precipitation and drought intensity. This sort of complicated pattern may occur for other climatological variables as well.

So what does this mean for “freak” late winter snowstorms in the southeastern United States? Climate change trending towards warmer temperatures makes frozen precipitation less likely (Figure 2), but given the variability inherent in meteorological systems (Figure 1), I wouldn’t rule it out entirely. But the snowshoes in my garage are still feeling a bit neglected.