Medecins Sans Frontieres, American Red Cross, and the UN are accepting donations for tsunami relief. This was the highest magnitude earthquake to hit Japan in recorded history, and the fifth highest magnitude quake in the history of the world. Based on geological histories and seismic data, 8 of the 10 highest magnitude quakes in human history have occurred in the last 60 years.
I don't know what caused the Sendai tsunami, but I do know that climate change creates a greater risk of earthquakes and tsunamis like this one. Changes in the atmosphere correlate with changes in the geosphere. As the planet warms due to carbon emissions, the higher global temperatures will lead to more seismic activity in two ways. First, rapid glacier melt changes the amount of pressure on the Earth's crust at given points, and leads to seismic "bounces" and shifts. Sudden shifts in coastal glaciers ("sudden" for glaciers meaning over 1km/year) create seismic waves that can cause tsunamis. And on the ocean floor, crystallized methane deposits can also melt when global temperatures rise, causing undersea landslides across intercontinental regions of the ocean floor that also trigger massive tsunamis.
This is a new area of study. The first scientific conference on climate forcing of geological hazards was in September 2009, hosted by University College London (Reuters coverage: Global warming may bring tsunami and quakes: scientists). The conference's press release had a good description of the idea:
Evidence from the past reveals that times of dramatic climatic change are also characterised by elevated geological activity. This is best demonstrated during the Holocene period (the last 10,000 years), during which climbing temperatures, melting ice and rising sea levels – following the end of the last ice age – triggered a vigorous response from the Earth’s crust.
Most notably, this included a significant rise in the level of volcanic activity as ice loss and ocean loading modified the stresses acting on volcanoes at high latitudes and altitudes and around the margins of the oceans. Other effects included rises in seismic activity in previously glaciated areas, in some places – for example off the coast of Norway – triggering gigantic submarine landslides and resultant tsunamis.
Undersea methane deposits and tsunamis
Papers for the conference were published by Royal Society A in a theme issue of their journal. There's a paywall on the full papers, but you can read the abstracts online to form your own opinion about the peer-reviewed research. This is from the editorial preface, by Bill McGuire:
The sensitivity to climate change of gas hydrates, in both marine and continental settings, has long captured interest, in relation to its potential role in past episodes of rapid warming, such as in the Palaeocene–Eocene thermal maximum (PETM), and in the context of anthropogenic warming. In the first of a pair of papers on the subject, Maslin et al. review the current state of the science as it relates to gas hydrates as a potential hazard. The authors note that gas hydrates may present a serious threat as the world warms, primarily through the release of large quantities of methane into the atmosphere, thus forcing accelerated warming, but also as a consequence of their possible role in promoting submarine slope failure and consequent tsunami generation.
. . .
Looking forward, one of the potential hazards presented by gas hydrates is their possible role in the destabilization of submarine slopes. This is one theme addressed by Tappin within a broader review of submarine mass failures (SMFs) as tsunami sources that incorporates the climate dimension. Tappin highlights the importance of climate in ‘preconditioning’ sediment so as to promote instability and failure, including its influence on sediment type, deposition rate and post-depositional modification. The author also notes that climate may play a role in triggering SMFs via earthquake or cyclic loading associated with tides or storm waves. Tappin makes the important point that, in the past, climate influence on SMFs appears to have been greatest at high latitudes and associated with glaciation–deglaciation cycles, which had a significant influence on sedimentation, preconditioning and triggering. As a corollary, Tappin notes that, as the Earth warms, increased understanding of the influence of climate will help to underpin forecasting of tsunami-sourcing SMFs, in particular at high latitudes where climate change is occurring most rapidly.
Methane hydrate in melting permafrost terrain can be introduced into the atmosphere. Methane gas is a much more powerful greenhouse gas than carbon dioxide, trapping more heat with a larger and more complex molecular structure than CO^2. There are methane deposits near the polar ice caps, but there are also methane deposits under the ocean floor at lower latitudes. If these are released, they can cause submarine landslides and slope collapses along the ocean floor, on a much larger scale than "subaerial" landslides, that cause extreme tsunamis. Imagine a mountain range collapsing in on itself over time, not just an isolated shift in tectonic plates. Since these methane deposits are located more heavily in the higher latitude crust, near the poles, these areas experience more tsunamis and earthquakes as the methane is released.
Sudden glacial melt and tsunamis
Several papers from the conference study the effects of glacial melt on the Earth's crust. Again, from McGuire's preface:
There is strong evidence for a crustal response to the rapidly changing post-glacial climate being elicited by load changes, either as a consequence of unloading at high latitudes and high altitudes due to ice-mass wastage, or as a result of the loading of ocean basins and continental margins in response to a 100 m or more rise in global sea level.
. . .
Continuing the theme, Hampel et al. take a broader look at how faults have responded to variations in ice and water volumes as a consequence of past climate change. Using numerical models, the authors demonstrate that climate-driven changes in ice and water volume are able to affect the slip evolution of both thrust and normal faults, with—in general—both the slip rate and the seismicity of a fault increasing with unloading and decreasing with loading. Adopting a case-study approach, Hampel and colleagues provide evidence for a widespread, post-glacial, seismic response on faults located beneath decaying ice sheets or glacial lakes. Looking ahead, the authors point to the implications of their results for ice-mass loss at high latitudes, and speculate that shrinkage of the Greenland and Antarctic ice sheets as a consequence of anthropogenic warming could result in a rise in the frequency of earthquakes in these regions.
When tectonic plates have large glaciers sitting on them, they don't truck around and butt into each other as much because they're weighed down. As those glaciers melt, the plates become more unstable, and you start to see more activity and "slip" along fault lines. When these glaciers are located in coastal regions, the relatively sudden shift can cause seismic waves that generate tsunamis. Again, since there are more glaciers in higher latitudes, these areas have historically experienced more seismic turbulence as those glaciers melt. Glaciers also occur at high altitudes at any latitude, and seismic activity increases in equatorial and tropical mountain ranges that are suddenly no longer weighed down by massive ice loads. The geological record also indicates that volcanic activity increases when glaciers recede and the Earth's crust becomes more unstable.
So the Earth's climate interacts with the Earth's crust on several levels. The exchange of underground and undersea gases with atmospheric gases, such as carbon dioxide in fossil fuel deposits and methane in hydrate deposits, and the interplay of that exchange with global temperate variation, links the two systems at a chemical and molecular level. Due to the influence of temperature, this activity is more frequent and intense as you move away from the equator towards the planet's poles.
By studying the history of the polar crust from the last ice age to today, we can see how the Earth's crust changes over the long term in relation to rising temperatures. In the planet as it is now, water tends to form into glaciers everywhere except a low-altitude blanket of warmth near the equator, where the Sun's rays meet with the dense atmosphere of gases that builds up at the Earth's lower altitudes. As a result, these low-altitude and low-latitude regions experience climate-driven geological hazards at a lower frequency.
These are the widely recognized and established mechanics of planetary science. The Earth's crust and Earth's climate are part of the same geochemical system, and events in one are codetermined by events in another. If a very high amount of heat is introduced into the Earth's climate at a rate that has not been seen in measured geological history, there will inevitably be related consequences in the Earth's crust. What these consequences are is largely unpredictable, but by looking at the changes that the Earth's crust underwent as the planet moved out of the last ice age to today, we can see that earthquakes, tsunamis, landslides, and volcanic eruptions are more common in times of warming, when glaciers are melting and greenhouse gases are rapidly escaping into the lower atmosphere.
"Skepticism" of these basic scientific theories has already started spreading in response to the tsunami, and stories in the science press about the relationship between tsunamis and climate change. Some fun examples:
Idiot global warming fanatics blame earthquake on climate change - Rick Moran, American Thinker (apparently not ironic)
It Begins...The Left Blames Earthquake, Tsunami on Global Warming - Anonymous, FOX Nation (tellingly filed under "Culture")
Some respond to Japan earthquake by pointing to global warming - Amanda Carey, The Daily Caller (warning: here be creationists)
And points for best headline in a science-distorting blog post goes to:
Massive Japan Earthquake Blamed on Cow Farts - "The Jawa Report"
