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Benjamin McKeown

Tropical Cyclones - 0 views

www.tulane.edu/...tropical_cyclones.htm

hurricanes hazards

shared by Benjamin McKeown on 17 Sep 14 - No Cached
  • In the western Pacific they are called typhoons, and in the southern hemisphere they are called cyclones.  But, no matter where they occur they represent the same process.
  • Tropical cyclones are dangerous because of their high winds, the storm surge produced as they approach a coast, and the severe thunderstorms associated with them. Although death due to hurricanes has decreased in recent years due to better methods of forecasting and establishment of early warning systems, the economic damage from hurricanes has increased as more and more development takes place along coastlines.
  • Warm ocean waters (of at least 26.5°C [80°F]) throughout about the upper 50 m of the tropical ocean must be present.  The heat in these warm waters is necessary to fuel the tropical cyclone. The atmosphere must cool fast enough with height, such that it is potentially unstable to moist convection. It is the thunderstorm activity which allows the heat stored in the ocean waters to be liberated and used for tropical cyclone development. The mid-troposphere (5 km [3 mi] altitude), must contain enough moisture to sustain the thunderstorms. Dry mid levels are not conducive to the continuing development of widespread thunderstorm activity. The disturbance must occur at a minimum distance of at least 500 km [300 mi] from the equator. For tropical cyclonic storms to occur, there is a requirement that the Coriolis force must be present.  Remember that the Coriolis effect is zero near the equator and increases to the north and south of the equator.  Without the Coriolis force, the low pressure of the disturbance cannot be maintained.
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  • There must be a pre-existing near-surface disturbance that shows convergence of moist air and is beginning to rotate. Tropical cyclones cannot be generated spontaneously. They require a weakly organized system that begins to spin and has low level inflow of moist air. There must be low values (less than about 10 m/s [20 mph]) of vertical wind shear between the surface and the upper troposphere. Vertical wind shear is the rate of change of wind velocity with altitude.  Large values of vertical wind shear disrupt the incipient tropical cyclone by removing the rising moist air too quickly, preventing the development of the tropical cyclone. Or, if a tropical cyclone has already formed, large vertical shear can weaken or destroy it by interfering with the organization around the cyclone center.
  • unstable atmosphere
  • his instability increases the likelihood of convection, which leads to strong updrafts that lift the air and moisture upwards, creating an environment favorable for the development of high, towering clouds.
  • Surface convergence (indicated by the small horizontal arrows in the diagram below) causes rising motion around a surface cyclone (labeled as "L"). The air cools as it rises (vertical arrows) and condensation occurs.  The condensation of water vapor to liquid water releases the latent heat of condensation into the atmosphere. This heating causes the air to expand, forcing the air to diverge at the upper levels (horizontal arrows at cloud tops).
  • Since pressure is a measure of the weight of the air above an area, removal of air at the upper levels subsequently reduces pressure at the surface. A further reduction in surface pressure leads to increasing convergence (due to an higher pressure gradient), which further intensifies the rising motion, latent heat release, and so on. As long as favorable conditions exist, this process continues to build upon itself
  • When cyclonic circulation begins around the central low pressure area, and wind speeds reach 62 km/hr (39 mi/hr) the disturbance is considered a tropical storm and is given a name.  When wind speeds reach 119 km/hr (74 mi/hr) it becomes a hurricane.
Benjamin McKeown

Admit it: we can't measure our ecological footprint | New Scientist - 0 views

www.newscientist.com/...asure-our-ecological-footprint

ecological footprint

shared by Benjamin McKeown on 01 Oct 15 - No Cached
  • “when humanity exhausted nature’s budget for the year” and began “drawing down local resource stocks and accumulating carbon dioxide in the atmosphere”. This year it was on 20 August, the earliest date yet.
  • “so misleading as to preclude their use in any serious science or policy context,” it says in a paper in PLoS Biology.
  • The footprint analysis does not really measure our overuse of the planet’s resources at all. If anything, it underestimates it.
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  • It does this by measuring the productive land and sea area available – cropland and pasture, forests and fishing grounds – and matching that against the demands placed on them. This biological accountancy system concludes that planet Earth has a biocapacity of 12 billion hectares, and a human demand equivalent to 18 billion hectares. Hence the 1.5 Earths figure. Our footprint is 50 per cent too big.
  • I had assumed that the analysis assessed the damaging environmental consequences of how we use the land – things like soil erosion and the overuse of water reserves. But no. It only measures land area.
  • “Local ecosystem abuse is a significant problem [but] to make reliable adjustments would require data sets that do not exist,” he writes. Or, as he told me: “Our current accounts cannot include soil erosion. Hence cropland use equals cropland availability.”
  • It uses UN statistics to compare the timber we harvest against annual growth. The conclusion is that, while we are deforesting some areas, growth elsewhere more than makes up for the loss. This is reflected in a surplus in the accounts.
  • If the calculation is to be believed, while some fish stocks are being over-exploited, a greater number are under-exploited and overall fish biomass is increasing. That’s another surplus
Benjamin McKeown

El Nino and extreme weather will be a theme of 2016 - 0 views

www.slate.com/...r_will_be_a_theme_of_2016.html

el nino

shared by Benjamin McKeown on 08 Mar 16 - No Cached
  • In fact, it’s probably the strongest that’s ever been measured. I
  • In fact, due to an atmospheric lag, extreme weather will likely keep getting worse for several more months. Though El Niño is typically the most powerful player among the world’s constantly feuding meteorological morphologies, it takes months for its burst of heat to filter around the globe from the tropical Pacific. Ocean temperatures in the El Niño regions of the Pacific usually peak in November or December, but globally-averaged temperatures don’t typically peak until between February and July of the following year.
  • Though El Niño is the proximate cause of many of this year’s weather records, its effects are an upward wiggle on top of the slow-rolling steamroller of climate change.
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  • Nearly 100 million people worldwide are facing food and water shortages this year due to drought and floods linked to El Niño.
  • current
  • El Niño is also helping to spread vector-borne diseases, like Zika, malaria, and dengue fever. And all the crazy weather is creating an uncertain economic environment, too.
  • been a few Florida tornado outbreaks th
  • This is what weather chaos looks like. Thankfully, climate scientists are using this rare event to learn as much as they can about what the super El Niño might tell them about future events and climate change—like in coral reefs, which are especially threatened this year.
  • his El Niño will transition to a La Niña—featuring an unusually cool patch of tropical Pacific waters—by late this year.
Benjamin McKeown

THE POLITICS OF CLIMATE CHANGE EXPLAINED - Lawrence Anthony Earth Organization - 0 views

www.earthorganization.org/cs-of-climate-change-explained

climate change kyoto

shared by Benjamin McKeown on 08 Sep 16 - No Cached
  • More than 150 nations signed it back in December 1997 at a meeting in Kyoto.
  • eorge W. Bush was installed as President soon afterwards, and announced that he was pulling the US out of the deal altogether. Since the US is the source of a quarter of emissions of greenhouse gases that was a big blow, but the other nations decided to carry on and they finally reached agreement in Marrakech in November 2001.
  • ndustrialised nations have committed themselves to a range of targets to reduce emissions between 1990
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  • he base year, and 2010.
  • an average 8 per cent cut for most of Europe to a maximum 10 per cent increase for Iceland and an 8 per cent increase for Australia.
  • European Union have agreed to share out their entitlement
  • atification of the treaty in national legislatures.
  • “flexibility mechanisms”
  • meet some targets by encouraging the natural environment to soak up more CO2 rather than by cutting emissions.
  • carbon sinks”
  • qualify for carbon credits by planting forests that soaked up CO2.
  • It was finally agreed that countries will be able to claim some carbon credits for planting forests in developing countries. And they will also be able to allow countries to claim credit for activities such as soil conservation, which will allow more carbon to be soaked up in soils.
  • carbon trading
  • But the fear is that some countries may find themselves with spare credits to sell just because their economies have slowed down, which would undermine the whole purpose of the protocol.
  • hot air”. Japan, Canada and perhaps others would like to buy up Russia’s spare permits.
  • But sceptics still see hot-air trading as a Trojan Horse for undermining the protocol.
  • lean Development Mechanism. This allows industrialised countries to claim credit for various activities in developing countries. It could become a major engine for getting clean energy technologies into poorer countries, so heading them off the dirty path to industrialisation that the rich nations took.
  • And the rules are biased towards small energy projects – solar cell systems, for exampl
  • he protocol allows industrialised countries to plant “carbon sink” forests in the tropics, for instance, where they will grow faster. They can also invest in clean energy technologies in the developing world, and claim carbon credits for doing so.
  • The US has demanded, both before and after Kyoto, that developing countries should accept their own specific emissions targets
  • it was intended to cut emissions by industrialised countries by an average of slightly over 5 per cent by the year 2010
  • hard to police, particularly the clauses on carbon sinks.
  • at perhaps 1.5 per cen
  • Will the Kyoto measures solve the problem of global warming? They will hardly scratch the surface. T
  • say it will buy us 10 years at most
  • . A reasonable target might be twice pre-industrial levels, which works out at 50 per cent above today’s levels.
  • Cutting emissions by 60 per cent is a suggested figure.
  • The Kyoto Protocol was drawn up with the long term as the primary focus. In essence, the protocol assumes that what we really need to worry about is the climate in a century’s time, not today.
  • CO2 sticks around for about a century. Methane, the second most important greenhouse gas, generally lasts in the atmosphere for about a decade. But while it’s there it is many times more potent.
  • This “hundred-year rule” has the effect of downgrading the importance of methane, and giving only small credit to countries that try to cut methane emissions.
  • the protocol gives a country that reduces its methane emissions by a tonne 20 times as much credit as for reducing CO2 emissions by a tonne.
  • Cows can be given less gas-inducing feed. Leaks in gas pipelines can be plugged. And so on.
  • Technically, we are going to have to find many more ways of producing energy without burning fossil fuels – the so-called carbon-free economy. Politically, we are going to have to find a way of doing so which doesn’t affect the growing economies of the developing nations, whose responsibility for the build-up of greenhouse gases so far has been minimal. Some people think this will require moving towards equal pollution rights for every citizen on the planet, a policy endorsed by Britain’s Royal Commission on Environmental Pollution earlier this year.
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