Indian Ocean climate impacts

In the recent post regarding the continuing impacts of Cyclone Nargis, I noted some unusual behaviour in the Indian Ocean SST. In particular, I noted that we are quite possibly headed into an apparently unprecedented third consecutive occurrence of the so-called Indian Ocean Dipole.

This behaviour of the IOD has not only been observed during the last few years, but is also a part of a longer trend of the past decades. The years 1994 and 1997 saw unusually strong positive IODs (e.g. this time series to 1990); 2006 was a moderate to strong event and this year remains to be determined...

In recent days, several instances of the impact of the Indian ocean have been noted. Both short- and long(er)-term impacts are noted.

The first item notes that tuna catches across the Indian Ocean have fallen sharply in the last two years and early indicators for this year show catches to be markedly below recent averages. Conservationists blame years of unchecked exploitation while processors say climatic conditions may be driving the fish deeper away from their nets.

As before, this illustrates the complexity of environmental problems and the difficulty of assigning ultimate cause and effect (and hence legal blame punishable by lawsuits). There are merits to both sides of the argument, and the reality of the situation is some nebulous gray between the two extremes. Years of overfishing have undoubtedly occurred and weakened the population, making it more susceptible to an unusual climatic event.

The recent IOD behaviour and The timing of the fishing loss event provides strong circumstantial evidence in favor of a climate effect. Normally a negative dipole follows a positive event. Fish populations are affected by changes in ocean conditions (El Nino was known for years by Peruvian fisherman for its impact of the anchovy haul, and the first(?) 'ENSO' paper explicitly linking ocean and atmosphere appeared in a tuna fishery journal...) and breaking the 'regular cycle' with the recent double IOD may have disrupted the fish's recovery. A triple positive IOD event could prove a disaster for Indian Ocean fisheries, hastening the inevitable end from overfishing.

The second item notes a recent study which identifies a link between a warming Indian Ocean and less rainfall in Africa. Rainfall in eastern Africa during the rainy season, which runs from March through May, has declined about 15 percent since the 1980s. Declines in rainfall in Ethiopia, Kenya, Tanzania, Zambia, Malawi and Zimbabwe were linked to increases in rainfall over the ocean.

Using both diagnostic (to identify how the observed decline work) and predictive modeling, the authors suggest "We can be quite certain that the decline in rainfall has been substantial and will continue to be. This 15 percent decrease every 20-25 years is likely to continue."

The study also notes that with current trends in emissions and local agricultural capacity the number of undernourished people could increase by more than 50 percent in eastern Africa by 2030. Coupled with the fishing problems noted above, the region looks set for continued troubles for years as a result of climate change.

A few final thoughts. As I've hinted at before (see also this post at Atmoz), these seemingly natural (but unusual) events are not caused by climate change, rather they are the climate change. This is how climate change manifests itself: increasing climate instability and an 'exaggeration' of normal behaviour.

The atmosphere and ocean radiate and stir, flux and transport, edging towards equilibrium, while never fully achieving it. This is in response to myriad of climate forcings on a variety of time scales. The forcing from a slowly-varying orbit and a reasonably well-behaved Sun has brought a certain dynamic equilibrium to the climate in recent millennia. Unfortunately, the relentless radiative forcing from the Great CO2 Enhancement Experiment is particularly large at this moment in Earth's long history and is driving the Earth's climate system in new ways (releasing the stored solar energy of millions of years in a century will do that...).

We are witnessing but the beginning of a long process of change; there are no stopping points in the immediate future. The CO2 already in the atmosphere will remain* for 100 years or so, committing us to a lengthy period of climate instability. Continuing the emissions of CO2 just adds to the forcing and drives the Earth systems harder, resulting in more chaos. These events in the Indian Ocean are just a foretaste of things to come.

*barring the unlikely event of successful geo-engineering project or some such...

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Image: Extracted from Africa: Atlas of our Changing Environment

Dissonant spheres

The 'spheres' of our planet have long acted harmoniously, brilliantly improvising off the others' riffs to produce a beautiful soundscape – the ecosystem we currently inhabit. The song started slowly and took a long time to reach it's present state, each new instrument gradually incorporated into the greater whole. The newest members sit in with the band are modern humans. Unfortunately, we play our instruments poorly and we have a tin ear. We are creating dissonance.

In many ways, the ocean (hydrosphere) can be considered the rhythm section, a solid foundation on which to base a composition. Water is essential to all life as we know it. This sphere is slow to act, but difficult to stop once it begins. The raucous caterwauling of humans is beginning to be noticed. A recent study shows that only 4% of the oceans remained undamaged by human activity. The oceans are becoming rapidly transformed through increasing temperature and acidity of seawater. There is some concern that we may have already triggered an ocean circulation collapse. Plastic rubbish covers vast stretches of the Pacific Ocean, detritus from our way of life.

The atmosphere is deeply influenced by the ocean (although the influence really goes both ways...). The El Nino-Southern Oscillation (ENSO) is a major factor in determining the weather. We are currently observing the peak of the La Nina phase of the cycle, wherein cooler-than-normal sea surface conditions prevail across much of the Pacific Ocean. This has broken an extended drought across eastern Australia, while simultaneously bringing 'the worst drought in decades' to Chile. The relations have been seen historically. The role of La Nina as opposed to general climate change in producing the unusual winter weather in China and the US is uncertain, and despite the claims of these articles cannot be determined right now; the data just aren't there. It is certainly possible, but more expected during the warm El Nino phase.

The biosphere –- living things – are the main melody in this music of the spheres. Without a melody, the song (often) isn't worth listening to. Human cacophony is increasingly disrupting the main theme. Anoxic dead zones in the ocean are on the increase, a result of global warming. Warming conditions are leading the increased migration of animals. In the UK, seabirds are facing threats as snake pipefish, virtually unknown before 2002, move into the area. Warming seas around Antarctica also threaten the invasion of predators -- first crabs then sharks -- into the fragile ecosystem of the the region, threatening widespread devastation. It's not just climate change; tuna fisheries are facing a massive collapse from overfishing.

Playing a supporting role on human time scales is the lithosphere (the Earth's crust). Global warming may lead to an increase in earthquakes and volcanic eruptions. Such ideas are very speculative, but do have some precedence – parts of the crust are still rebounding' from the removal of ice from the last ice age. Probably a coincidence, but Norway just recorded its strongest earthquake ever in its Arctic archipelago.

It's obvious from the above that humans are not the virtuosos we imagine ourselves to be. We continue to belt out our drunken karaoke version of “My Way” at our own peril; the band may pack up and go home. Following the sentiment of Miles Davis, It's not the notes you play, but rather the space between the notes that make the music. Listening carefully and playing appropriately are admirable qualities. Silence is a perfectly acceptable musical technique; something is always happening that makes a sound. Seeing our selves and our species as a part of nature; fitting in and living within the more-than-adequate limits provided by the ecosystem. This philosophy will go a long way towards helping humanity produce a lasting grand opus.

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Image: I. Stravinsky, L' Sacre du Printemps