For the past two years, a thickening, heating, drying atmosphere over Brazil has become the haunt of one of the worst kinds of atmospheric bullies. A blocking high that has parched an already wounded forest country, shrinking its reservoirs, turning rivers into ribbons, and threatening millions with a lack of access to essential water.
The block feeds on heat and the building inertia of a warming atmosphere (see also Quirky Winds Fuel Brazil Drought). It is a new species of mutant weather animal bred by human caused climate change. Its ilk have ranged the globe setting off terrible droughts in places like Syria, California and Southeast Asia. But perhaps nowhere is the undoing of rain so strange and tragic as it is for water-rich Brazil.
Amazon Rain Forest. The very name conjures the image of lush vegetation, of mists, of rivers of storms riding the thick, moisture-laden airs. A wet interplay of forest and atmosphere that has for centuries reinforced and amplified the cycle of drawing life-giving water down from the skies.
But no more. Human climate change, a regional deforestation mafia, and the ogre of a blocking high pressure system gorged on heat steroids have put an end to that.
(The rainy season that wasn’t. NOAA map shows much depleted wet season for 2013-2014 and 2014-2015. Image source: NOAA.)
For as of last week, reports from NOAA showed a rainy season 2/3 past and desperately dried and behind schedule (see image above). A ‘rainy’ season in which large swaths of Brazil and the Amazon Rainforest fell into the lowest percentile of years for moisture received.
And the dry 2014-2015 ‘wet season’ comes just following the equally moisture lacking 2013-2014 ‘wet season.’
Will the Rains Briefly Return?
For the Sao Paulo region, at the epicenter of the current blocking pattern and deforestation induced drought, 2014 was the driest year since record keeping began in 1930 (see Drought in Sao Paulo). 2015, so far has only seen slightly more water. And the slight increases in rains have only been enough to push Sao Paulo’s largest aquifer — the Cantariera — to 12.9 percent capacity, even when dead pool volumes are included (without the new dead pool volume, Cantariera would be sitting around 9 percent).
With a little more than a month and a half remaining to a notably stunted rainy season, the Cantariera will be fortunate to hit 1/5 capacity by late April. A situation which could see the most populated region in Brazil desperately shy of water and continuing current rationing at least for the next year.
However, a newly emerging Pacific El Nino may draw back on current moisture flows to the region, putting a lid on late season rainfalls and pumping up the blocking high yet again (see ENSO and Drought Forecasting). If the forecast rains do not arrive and the block again tightens its grip over the region, Sao Paulo could be looking at running out of water for many of citizens over a 4-6 month period.
Megadrought For The Deforest
Regardless of whether a brief spate of rainfall provides new hope for avoiding a complete collapse of Sao Paulo’s water supplies for 2015, the long term situation looks increasingly dire. Added heat from human-caused warming combines with rampant deforestation in Brazil to create a kind of drought death spiral. Already baking under the heat of an equatorial sun, the clear-cut and burned Amazon is now struggling to retain moisture. Understory fires and gradually building heat due to human warming at the rate of 0.25 C per decade for the rainforest provide additional stress to a critical forest region.
(2013 JPL study found that climate change was weakening the Amazon’s ability to recover from severe droughts like the one seen in this 2005 moisture anomaly capture. Under human caused climate change, droughts become far more frequent and intense. A 2009 study found that 85% percent of the Amazon would likely be lost due to climate change alone at 4 C of warming. Even mild warming of slightly more than 1 C could result in additional losses of 20-40 percent.)
A recent report in The Economist estimates that 30,000 new trees would need to be planted to help rejuvenate the ‘flying rivers’ that continuously feed moisture to the rainforest (a very low number considering the fact that the Amazon contains an estimated 390 billion individual trees divided into 16,000 species). Deforestation, as well, would necessarily have to stop. And even if these two requirements were met, human caused warming would have to be quite mild to spare the Amazon conflagration and conversion to much drier savannah and grasslands.
Given these dire challenges, it must be assumed that Brazil, much like the US Southwest and other regions of the world faces the prospect of potential megadrought over the coming years and decades. So what we are seeing for Sao Paulo now is, sadly, prelude.