Introduction to Climate Systems (Week 2) - Post 2

Week 2 - Introduction to Climate Change

          The global climate is warming because of the relationship between Earth’s systems and human emissions.While the threat of global warming considers climate change in the last one hundred years, the Earth’s environment has always been changing, scientists know that because of the Milankovitch Cycles. These cycles help scientists understand the periods of global warming and cooling that have happened in our climate over the past 1 million years. The Earth’s eccentricity, which changes every 100,000 years is the shape of Earth’s orbit, and it shows us the different rates of solar energy the Earth receives when it’s at its closest to the sun, the perihelion, versus when it’s at its farthest from the sun, the aphelion. The Earth’s obliquity regards the tilt of Earth’s axis, and it is on a 40,000 year cycle, this degree of the tilt accounts for the difference in seasonal temperatures. The Earth’s precession is the direction of the Earth’s axis, this determines which hemisphere has what season when. The precession of Earth is on a 26,000 year cycle. All of the Milankovitch cycles show scientists the cause of the regular periods of warming and cooling the Earth goes through over millions of years. Now to look at current climate warming, the thousands of different systems that make up Earth’s ecosystem must be considered. Each system has their own stocks, flows and loops. Each of these systems exists in a cycle between the amount of matter, the stock, and the things that affect the growth or decay of that matter, the flow. The correspondence between the stock and the flow can either be amplifying or stabilizing. A stabilizing feedback loop will always balance itself out at the original rate whenever either the stock or flow increases. An amplifying feedback happens when the increase of stock causes a further increase of flow and vice versa. The Earth’s ecosystem is essentially a giant amplifying feedback loop. The ecosystem has what is called a climate sensitivity number; for every 1 watt/m^2 energy increase, Earth’s climate temperature will increase ¾ of a degree. A watt is the measurement of Joules/second, joules is the way scientists quantify energy. In this case joules represent solar energy or energy from the sun. So a watt/meter^2 is the measurement of Earth’s intake of solar energy per second per meter squared. If Earth’s energy intake were to go up by 4 watt/m^2, because of the climate sensitivity number, scientists can calculate Earth’s surface temperature will increase by 3 degrees globally. Now in order for the energy to increase by 4 watt/m^2 societies CO2 emissions’ must be called into question. Each time society doubles the amount of CO2 in the atmosphere it increases the energy by exactly 4 watt/sec^2, which means every time the the CO2 is doubled, the  global temperature rises by 3 degrees. Through scientific data scientists' have determined that this temperature increase is not far off, humans are well on their way to doubling the global amount of CO2 in the atmosphere. That relationship between CO2 emissions and global temperature is the giant amplifying feedback loop that exists in our ecosystem. This is what scientists mean when they talk about climate change or global warming. Increased CO2 creates an increase of heat energy in the atmosphere, because it traps the incoming heat from going back out to space. In other words the heat energy is the stock, and the CO2 is a perturbation of the system that causes the inflow of energy to now be larger than the outflow. Now an increase of 3 degrees globally may not seem like much, however even a small change in the temperature can cause a wide range of catastrophic events. Global temperature increase causes a host of problems including: sea level rise, melting of arctic sea ice, warmer oceans which cause coral reefs to die, we’ve already killed a quarter of the coral reefs in the last 30 years, an increase in catastrophic floods, droughts in already warmer areas, heat waves, ecosystem change, which causes species to die, decrease in agricultural yield, and many other issues.

          All of the aspects of climate systems and what makes them grow, change, and affect things is correlated through climate change. Whether it be climate changes over the past million years, or current climate changes that have happened over the past hundred years. Everything humans do affects the ecosystem, and because the ecosystem is an amplifying feedback loop, a lot of the time people aren’t aware just how much damage a seemingly small change can do.