4.4 IB Biology

A4.4.3: Evaluating claims that human activities are not causing climate change.

Evidence clearly shows temperature increases since the industrial revolution. Extreme weather events, record temperatures, and receding glaciers are being confirmed day after day. Climate change is not a debate or a controversy; it is well-supported by an increasing volume of data.

U4.4.8: Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.

As previously discussed, greenhouse gases lead to an increase in global temperatures. The number one activity that is contributing to the increased amount of atmospheric CO2 is the combustion of fossil fuels for transportation. Additional activities that increase greenhouse gases include the burning of forests, diets that are high in meat, purchasing goods produced great distances away, long commutes, and purchasing foods out of season. Methane is increasing as a result of the raising of livestock for meat production. Nitrogen oxides are also increasing, with sources including the combustion of fossil fuels, organic and commercial fertilizer use, and industrial processes.

U4.4.2: Other gases including methane and nitrogen oxides have less impact.

Comparing the gases, some interesting trends can be seen: The concentration of carbon dioxide in the atmosphere is about 400 ppm, 200x greater than methane, and 1000x greater than nitrogen oxides. Methane can actually hold more heat, but its lifespan is only about 12 years before it decays into other molecules. Carbon dioxide lasts 50 - 200 years, and is fairly non-reactive. Nitrogen oxides have a warming potential of 100x that of carbon, but make up only about 320 ppb, while CO2 is at 440 ppm.

A4.4.1: Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.

Coral polyps are very sensitive to three things: water temperature, acidity, and depth. All of these factors are changing as a result of human activity. Dissolved carbon dioxide decreases the pH of the water, leading to the death of the polyps, indicated by the color of the reef becoming bleach white. Coral reef death affects the entire ecosystem by disrupting the food chain.

U4.4.7: There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures.

Prior to the industrial revolution, most people made products using hand tools. With the advent of factories and later transportation powered by fossil fuels, carbon dioxide concentrations in the atmosphere began to increase. Additionally, clearing and burning of forests to accommodate a growing population also contributes to the atmospheric CO2 concentration. It is estimated that in the past 200 years, humans have increased the CO2 concentration by about 35% when compared to pre-industrial revolution times.

U4.4.1: Carbon dioxide and water vapor are the most significant greenhouse gases.

The greenhouse effect is the tendency of the atmosphere to retain heat that originally came from the Sun. When sunlight comes to Earth, it is in shortwave radiation. As it comes into contact with the surface of the planet, it's transformed into another form of energy, heat. Heat has a much longer wavelength than light energy, and it becomes trapped by the atmosphere. This warms the planet, and is a natural phenomenon. The gases responsible for trapping the heat from the sun include carbon dioxide, water vapor, and to a lesser extent, methane and nitrogen oxides. Earth is currently experiencing a runaway greenhouse effect, which is contributing to global warming.

U4.4.6: Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.

There are many factors that influence the climate on Earth, including volcanic eruptions, solar radiation, oscillations in ocean currents and many other factors. However, there is strong evidence that an increased amount of carbon dioxide leads to an increase in temperature. Since carbon dioxide is a greenhouse gas, we know that it will trap solar energy and can increase the greenhouse effect. Over time, this can lead to increased temperatures, which causes oceans to release more carbon dioxide, increasing the temperature again, and so on.

U4.4.3: The impact of a gas depends on its ability to absorb long-wave radiation as well as on its concentration in the atmosphere.

Two main factors affect a gases' ability to influence the greenhouse effect The ability to absorb long-wave energy (heat) The concentration of that gas in the atmosphere

U4.4.5: Longer wave radiation is absorbed by greenhouse gases, which retain the heat in the atmosphere.

When sunlight comes into contact with matter, some of the energy is reflected back into space. Some of the sun's energy is absorbed and reemitted as long-wave infrared radiation (heat). Albedo is the ability of a surface to reflect light. Light colored objects have a high albedo, so they reflect more light and are cooler. Dark colored objects have a low albedo, and absorb more light, increasing their temperature.