Climate change is causing more and longer droughts
Mr Macauley's family has run the ranch since 1894, so they have learnt to live with the
perpetual water shortage in this desert state. But living off the land is becoming ever more difficult, because of higher temperatures and lower rainfall.
"The environment here is changing at a shocking speed. The summer has been coming a week earlier and staying a week longer," says Scott Harger, a
conservationist near Flagstaff, northern Arizona.
"We are always complaining that we do not get enough rain, but most people are able to sense that it is getting drier, and they are concerned about it."
Much of the US south-west has been in a drought since 1999, the most severe in more than a century, but it has been
exacerbated by record warming. The average temperature in the south-west has already increased by about 1.5°F above the average recorded between 1960-79, the US Global Change Research Program said in a recent paper.
It is projected to rise as much as 10°F by the end of the century, the programme says, as "human-induced climate change appears to be well under way in the south-west".
Just as global warming is affecting life in developing countries such as Bangladesh and the Pacific island of Nauru, where rising sea levels are
gobbling up land, so too is it affecting the richest country on earth.
Some studies estimate that the "dust bowl" drought conditions of the 1930s will become the norm in the south-west by 2050, and supplying the area with water will cost $950bn a year, almost 1 per cent of US gross domestic product.
Certainly, 2009 has been difficult. The winter was drier than usual. Then the monsoons that usually
drench the state each summer never arrived, leaving large areas to manage with less than half their average annual rainfall, says Gary Woodall, chief meteorologist in Phoenix.
"Compounding that, we have had very warm temperatures, even by Arizona standards," Mr Woodall says. "So we have had
a one-two punch of very low precipitation and very warm weather."
Rising temperatures are reducing the flows in the Colorado river, the south-west's lifeline, while fast-growing cities such as Phoenix
emit ever increasing amounts of carbon while demanding more and more water.
The water shortages affect ranchers the worst. In northern Arizona, a
pasture can cover as many as 90,000 acres, and some ranches run to almost 20 pastures, meaning
the likes of Mr Macauley can aim only to fill ponds. But farmers who are able to irrigate their fields are feeling the heat too.
Constant difficulties
"The difficulty of irrigating is constant," says Jim Hanness, who grows cotton,
durum wheat and forage for cows on his 710-acre farm near Casa Grande in southern Arizona.
"Am I worried about the drought we're in? Yes. Am I concerned about the amount of storage space [in dams] not filled? Yes. But I can't affect this - we live in a perpetual drought and we have gone to great lengths to use water very wisely," he says.
While conceding that water supplies are becoming more scarce and their state is experiencing increasing
desertification, many Arizonans who work the land are climate-change sceptics.
Both Mr Macauley and Mr Hanness blame the combination of Arizona's natural dryness and population growth for their water problems. "I can't quite buy the idea of global warming in its entirety," Mr Hanness says.
Even in academic circles, there is debate on how much the region's water shortages are the result of climate change and how much the result of unfavourable weather patterns.
"It's tricky to say that this is caused by greenhouse gases because the natural variability in this region is colossal. But certainly the drying is going to get worse and worse as the global climate warms up," says Richard Seager, a research scientist at Columbia University's Lamont Doherty Earth Observatory.
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