22 Jan 2014
Change is in the Air (and Water): Climate Change and Ocean Health
Climate change is the most all-encompassing of the five main ways that human activities are causing significant changes in the ocean. These five key 'drivers' -climate change; fisheries exploitation; habitat destruction; pollution by chemicals, excessive nutrients, pathogens, and trash; and the spread of invasive species -all interact, such that greater intensity of any one is likely to increase the adverse effects of the others.
January, the first full month of winter in the Northern Hemisphere and summer in the Southern, is an instructive time to think about climate change. There can be warm days in winter and cool ones in summer, but on average we all expect winter to be colder than summer. That average is what we call 'climate.' The changeable daily conditions are 'weather.' Climate is what you expect; weather is what you get.
But expectations are shifting; there is now overwhelming evidence and scientific agreement that Earth's climate is rapidly warming and that the cause is carbon dioxide (CO2), and other gases and particles emitted from the burning of large amounts of coal, oil, natural gas, and biomass (forests and fields).
The physics of global warming is simple and inevitable. Sunlight penetrates the atmosphere, heating up air, water, and land. At the same time CO2, particles and other 'greenhouse' gases form a blanket that traps heat and slowly warms the biosphere.
The increased heat evaporates more water, melts glaciers and sea ice, creates more clouds, alters wind and water currents, increases the frequency and intensity of storms and changes the patterns of rainfall worldwide.
The confusing thing is that while the whole planet is heating up on average, local climates are changing differently in different places. For example, the Arctic is heating up much faster than anywhere else. But just as some places warm, increased clouds, fog or changes in winds and current may cause cooling elsewhere. The inadequacy of 'global warming' and 'global climate change' to express this variability spawned the term, 'global weirding' to convey that change is in the air -and the water too- but with different surprises in store for different places.
Dramatic changes in climate occurred long before there were people. They were driven by changes in solar
radiance, variations in our planet’s orbit and axis, volcanism, seafloor
spreading and continental ‘drift’, differences in the relative balance between
land and sea in the different hemispheres and impacts from extra-terrestrial
objects such as comets or asteroids.
Those factors still operate, but the rate and magnitude of human-caused
change now exceeds their effects.
Why is everyone so concerned about climate change if it has happened before? Here’s why: Climate controls much of life. It is the environmental envelope within which nearly all living things exist. Climate warming or cooling--regardless of when, where or why--- has always brought enormous changes to life, some lasting centuries or millennia, others-- such as mass extinctions—global, catastrophic and irreversible.
If we cause climate warming, can’t we stop it? Yes, but not quickly. Once emitted, CO2 stays in the air for about 70 years; the amount that we have already released guarantees that warming will continue for many decades even if we stop adding more. Yet, reducing CO2 emissions is probably the only thing we can do. Alternative ‘geo-engineering’ proposals to cool the planet by making more sunlight-reflecting clouds, fertilizing the ocean to increase plankton plant populations and their biological uptake of CO2, or extracting CO2 from the atmosphere by industrial processes have not been shown to be practical and may be risky.
How is the ocean affected by global warming? First of all, warming is already changing the ocean’s physical structure by:
A further confounding factor is ocean acidification. About half of the CO2 that people have emitted into the atmosphere has been absorbed by the ocean,
slowing the rate of global warming, but increasing the ocean’s acidity by about
30%. Increased acidity reduces the
ability of clams, mussels, starfish, sea urchins, corals and many other marine
organisms to make calcium carbonate shells and skeletons, causing potential
harm to fisheries, mariculture, tropical and cold-water coral reefs, biodiversity---and
the human economies that depend on them. In addition to previously mentioned challenges, increased
temperature makes it harder for organisms to adapt to increased acidity and vice versa.
So, from a very simple beginning, excessive release of a common and
simple chemical, CO2, we have begun to affect nearly every aspect of
life in the ocean and elsewhere on Earth.
With all this in mind, you might wonder how the Ocean Health Index deals with these global change issues.
For example, why doesn’t the Index contain a goal or indicator for ‘marine climate change.’ For one thing, each of the Index’s 10 goals represents a benefit that people expect from a healthy ocean. Climate certainly affects the delivery of those benefits, but it is not itself a benefit True, the ocean buffers global and local climates, but that has nothing to do with its health, but only the physics of water. There are indicators and an index to measure the physical aspects of global climate change, as well as indices that measure nations’ progress in reducing CO2 emissions, but the bottom line is that there is no practical way to measure ‘global marine climate change’ in a meaningful, comprehensive way or to establish a reference point for it.
A comprehensive indicator that includes biological and economic
components seems almost unimaginably difficult owing to geographic variability and
the varied responses of the huge number of species. Even if it could be calculated, the indicator would move too
slowly and with too much variation to be instructive.
Instead of trying to make such a comprehensive indicator, the Ocean Health Index includes four aspects of climate change among the Pressures that affect the delivery of ocean benefits to people: Sea Surface Temperature, Sea Level Rise, Ultraviolet Radiation and pH (a measure of ocean acidification).
These four pressures, along with those caused by fisheries extraction, habitat change, pollution and invasive species, were ranked for their relative global impact within each goal, sub-goal or (when possible) goal component (e.g. specific habitat) as ‘high,’ ‘medium,’ ‘low’ or ‘no impact.’
Pressure from Sea Surface Temperature was judged to have high impact on corals and sea ice, medium impact on seagrasses and low impact on species and iconic species, so it primarily affected scores for Natural Products, Carbon Storage, Coastal Protection, Sense of Place and Biodiversity.
In similar ways, Sea Level Change affected scores for Mariculture, Natural Products, Carbon Storage, Coastal Protection, Tourism & Recreation Livelihoods & Economies, Sense of Place and Biodiversity, mainly through its effect on mangrove, coral, seagrass, saltmarsh and sea ice habitats and species or iconic species associated with them, but also through effects on ports and harbors operation and potential effects on renewable energy generation.
Ocean acidification affected scores for the same suite of goals as did Sea Surface Temperature, through its likely effects on corals, sponges, shells, seagrasses and species, all of which were ranked low.
Finally, Ultraviolet Light, which has some links to climate change, affected scores for Natural Products, Coastal Protection and Biodiversity, mainly through harmful effects on corals and associated species. All effects were ranked as low impact.
Climate change, global warming and global weirding will certainly continue through the lives of everyone reading this article and probably those of our children too. Even so, reducing emissions of CO2, particles and other greenhouse gases as quickly and dramatically as possible will reduce the harm they cause in the future and our descendents will thank us for it.