Climate Change Impacts and Natural Hazards
Evidence of Global Warming
Retreating glaciers (in recent decades, glaciers have receded, especially in the Northern Hemisphere, also affecting the ice or frost layer covering polar oceans, losing 40% of their thickness), rising sea levels (currently 3mm annually due to melting ice), increased global temperature (reflected in the above), more frequent extreme weather events (droughts, floods, and heat waves are more common), and living organisms modifying their behavior and distribution (migrations and habitat changes).
Factors Influencing Earth’s Temperature
Distance from the sun: Solar radiation determines the planet’s energy balance.
Atmosphere and its characteristics: Atmospheric composition: clean, dry air is 78% nitrogen, 21% oxygen, and 1% other gases (argon, CO2). It also contains water vapor, varying humidity, and suspended particles (aerosols), both natural and artificial.
Natural greenhouse effect: Our planet would be at -18°C without an atmosphere, but with it, we average 15°C due to natural greenhouse gases.
Greenhouse gases: Water vapor (the major contributor), CO2 (2nd most important), and methane.
How the Greenhouse Effect Works
Of the incoming solar radiation, 30% is reflected back into space by the atmosphere or land (albedo), 19% is absorbed by clouds and other atmospheric components, and 51% is absorbed by the Earth’s surface, increasing its temperature. This absorbed energy is then re-emitted as infrared radiation, which heats the air. Greenhouse gases trap some of this outgoing heat, maintaining a constant temperature. A balance exists between incoming solar radiation and outgoing infrared radiation.
Climates of the Past
Changes in sea level: Any global change affects the ocean by changing the water cycle and thermal expansion of water.
Factors Influencing Climate Change
External or astronomical causes: Changes in solar activity (the sun’s output modifies and affects Earth), changes in Earth’s orbit (the Earth’s elliptical orbit changes, modifying the radiation reaching Earth), meteorite impacts (a large meteor impact can create a dust cloud, preventing solar radiation from reaching the surface), changes in atmospheric composition (modifying the atmosphere’s composition changes the amount of solar radiation received), and changes in ocean currents (if thermohaline circulation is altered, global and North Atlantic temperatures decrease, increasing ice cover and thus albedo).
Alarming Rise in Greenhouse Gases
Most of these gases occur naturally, but their concentration has increased significantly since the Industrial Revolution due to burning fossil fuels (oil and gas used for energy), deforestation (removing vegetation reduces CO2 removal), and certain agricultural and livestock activities (cattle emit methane during digestion, some crops also contribute). Other greenhouse gases include ozone and N2O. Water vapor is the most abundant.
Increasing greenhouse gases cause Earth to warm.
Climate Model Predictions
+1.4-6°C increase in global mean temperature, 20-80 cm rise in global mean sea level, more frequent extreme weather events, and environmental and health effects.
Risks
Risk is the probability of a catastrophe affecting humans or property. Its value is determined by:
- The potential magnitude of the event and its frequency.
- Exposure: the amount and value of assets that may be affected.
- Susceptibility and vulnerability of a community to damage.
Besides natural consequences, human decisions play a role. Risks can be mitigated (taking measures to minimize the impact of an event) and predicted (using data to determine the likelihood and timing of an event).
Earthquake Risk
An earthquake is the vibration of the ground caused by the release of energy between rocks under stress. This movement can create fractures or faults. The hypocenter is the location where the earthquake originates. Seismic waves travel in all directions from the hypocenter. The epicenter is the point on the Earth’s surface closest to the hypocenter.
Measuring earthquakes: Seismographs measure ground motion. Magnitude measures the energy released (Richter scale, each level represents a 32-fold increase in energy; a level 6 earthquake is equivalent to one atomic bomb).
Where Do Most Earthquakes Occur?
Near plate boundaries:
- Ocean ridges (plates move apart, and new lithosphere is created).
- Subduction zones (lithosphere is destroyed as one plate slides under another, causing many strong earthquakes).
- Transform faults (lithosphere is neither created nor destroyed, but plates slide past each other laterally, causing large earthquakes).
Earthquake prediction: While precise prediction is impossible, factors such as plate boundary location, local geological features, and seismic history can help assess risk.
Seismic prevention: Earthquakes cannot be prevented, but seismic risk can be reduced through seismic maps and building codes.
Tsunami Risk
A tsunami is created when a deep-sea earthquake suddenly displaces a large mass of water. As the wave approaches the coast, it loses velocity and gains altitude.
Tsunamis travel quickly, propagate with little energy loss, and often cause a noticeable withdrawal of the sea before hitting the coast.
Tsunami risk in Spain: While low, a tsunami originating in Portugal affected Spain in 1755. Tsunami warning systems detect seafloor and sea surface motion and issue alerts.
Volcanic Hazards
The Canary Islands are the only volcanically active region in Spain.
Volcanic eruption dangers: Two types of volcanic activity exist: effusive (low-viscosity lava flows smoothly with few explosions) and explosive (viscous lava blocks vents, building pressure and leading to explosions and pyroclastic flows). Dangers include toxic gas emissions, pyroclastic flows, explosions, mudflows, and lava flows.
Volcano monitoring: Volcanic prediction is more reliable than earthquake prediction. Warning signs include small earthquakes, ground deformation, rising water temperatures in wells, and increased gas emissions.
Flood Risk
Floods occur when water inundates normally dry areas, often due to torrential rain. A hydrographic basin is the area of land where water drains into a single river. Surface runoff (water flowing over the ground) is a major cause of flooding.
Human influence: Human activities increase flood risk by occupying floodplains, deforestation, covering the ground with impermeable materials, and altering river channels.