Climate Change

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Global Warming §

• Earth’s average global temperature from 2015 to 2019 has risen significantly compared to a baseline average from 1951 to 1980
• Global warming is more significant in the Northern Hemisphere because of more land mass and less ocean
  • Regions that are experiencing cooling instead of warming are because of melting land ice and changes in ocean currents associated with global warming
• Temperatures in the U.S. have risen over the past 30 years compared to the average for the 20th century
• It’s usually 1-1.5 degrees Fahrenheit, which doesn’t seem significant at first. Until you realize its the ENTIRE planet that rose a degree. That’s a lot of energy
  • Lowering global temperature by 5 degrees Celsius is enough to put is in an ice age
• The rate of temperature rise is greater now than it has ever been in the Earth’s past
  • More than 1 degree C in the past 50 years, 10 times faster than anytime in the past 800,000 years
  • Large changes in temperature have occurred throughout Earth’s history and several times in the past hundreds of thousands of years we have been warmer. But Earth has never experienced such rapid increase in temperatures over such a short time period
• The thermohaline current is an ocean current that moves water around the globe and enables an exchange of water between the surface and deepest parts of the ocean. A major location where surface waters sink is next to Greenland
  • This affects water temperatures around the world
  • The thermohaline current brings warm gulf waters to the Northeast Atlantic which causes western Europe to have a warmer climate than Canada at the same latitude on the Eastern side of the Atlantic
  • Freshwater (which is less dense than saltwater) from melting Arctic ice prevents cold surface waters in the North Atlantic from sinking, slowing down the thermohaline current, leading to cooler temperatures in the North Atlantic. But this trend is not sufficient to undo global warming everywhere else in the northern hemisphere

The Components that Control Atmospheric Temperature §

• Large changes in the temperature throughput Earth’s history are not random - there are noticeable cycles on the order of 25,000, 40,000, and 100,00 years
• Global temperature changes are strongly influenced by changes in Earth’s orbital parameters
  • These are due to the Milankovitch Cycles
• Over the last 50 years the amount of energy the Earth has received from the Sun has remained the same and is currently decreasing, while temperatures have risen
• The Greenhouse Effect is the process by which visible sunlight is converted into heat (infrared light) some of which is then trapped in our Atmosphere
  • The Greenhouse Effect works by converted short-wavelength radiation (visible light) to longer wavelength radiation (heat) and trapping some of it
  • Visible light from the sun passes through glass
  • When shortwave radiation hits a surface, it excites the atoms which converts it to heat, which is reemitted as longwave radiation (infrared light)
  • Glass traps a good portion of the heat (longwave radiation/infrared light), causing the greenhouse to heat up
  • In our atmosphere, Greenhouse Gases allow visible light from the Sun to pass to the surface, but traps some of the reemitted infrared light (heat), causing the planet to warm. Just like a greenhouse
  • With greenhouse gases the average temperature on the Earth is 61 degrees Fahrenheit
  • Without greenhouse gases the Earth would average only 0 degrees Fahrenheit and become completely ice covered
  • So we kind of like greenhouse gases, they’re good and necessary for survival
  • Earth’s greenhouse effect is being intensified by human emissions of greenhouse gases
  • We greatly influence the greenhouse gases because only a small amount of the atmosphere is supposed to be greenhouse gases (like CO2) and we emit enough to change that percentage
  • Carbon Dioxide represents 3/4 of our greenhouse gas emissions each year
• Aerosols - small particles (natural or humanmade, liquid or solid) suspended in the atmosphere that block sunlight, thus causing global cooling (and pollution)
  • Natural aerosols include volcanic ash and sulfuric acid droplets from erupted sulfur dioxide gas, sea salt sprayed to the air, and dust and sand blown into the air
  • Examples
    • The 1815 eruption of Mt. Tambora caused global cooling of 0.5 degrees Celsius for a year
    • Sand blown off the Saharan Desert can cool Atlantic waters enough to prevent Hurricanes
    • Saltwater blown into the air evaporates leaving slat crystals to be carried by the wind
    • Wildfires, both natural and human caused, emit black carbon aerosols into the atmosphere
    • And of course, Sulfate emissions from vehicle exhaust burning fossil fuels are a big source of aerosols and pollution
  • Cleaning up vehicle exhaust and other aerosols could actually cause global temperatures to rise
• Albedo - the capacity of a surface to reflect light, which determines how much gets converted into heat
  • Ice helps keep our planet cool by reflecting sunlight because it has a high albedo and converts less sunlight into heat
  • Ocean water has low albedo and converts a lot of
  • Positive feedback effect - melting ice leads to more surface water, which leads to warmer temperatures, and thus more melting of ice

Quantifying Global Warming §

• The key to understanding past climates comes from ice cores
• In 2021 a massive crack broke off the northern part of the Brunt Ice shelf
  • After breaking off it melts much faster, and lets ice from the land flow to sea and melt faster
• The disintegration of the Larsen Ice Shelf really happened, but ice cores are never taken from ice shelves because the ice is too thin
  • The part that broke off was roughly the size of Rhode Island
• The ice over land is much thicker and we can drill very deep to see things from way further back in time
• Ice cores enable us to understand the relationship between past temperatures (from ice chemistry) and greenhouse gas concentrations (from trapped air bubbles)
• The deepest cores go down more than 3 kilometers to find ice continuously back to 800,000 years
• Ice cores show us that temperatures and CO2 concentrations are always closely correlated - when one increases, the other increases and vice versa
  • Over the past 250 years, the levels of CO2 have climbed much faster and much higher than any time in the past 800,000 years (longest continuous record)
  • This correlates to the start of the Industrial Revolution where we really started burning fossil fuels
• Scientists use computer models that simulate atmospheric models and ocean dynamics due to natural and human factors to determine what is responsible for current global warming
  • Atmospheric models lead to the unequivocal conclusion that human emissions of greenhouse gases are required to explain the current rise in global temperatures
  • Human emissions of greenhouse gases is the reason why our planet is getting hotter very rapidly

Climate Change §

• Climate Change refers to change sin climate due to global warming: hotter/cooler, wetter/dryer, increased frequency and severity of storms and wildfires
  • Climate change is a consequence of global warming
• Weather - the condition in the atmosphere of a particular place and time
• Climate - the weather over a broad area averaged over a long period of time
• If weather is your mood, climate is your personality
• Unusually warm weather in the Arctic due to global warming can cause unusually cold weather to the South
• Climate change brings on weather whiplash with quick swings between wet and dry or hot and cold periods
  • Over the past decade, California has gone from record drought to record rains, back to drought, and back to even higher record rains
• Climate change is all about extremes. Normal has become the exception
  • The number of thot and extremely hot days has jumped dramatically compared to pre 1980
• Consequences
  • Especially equatorial regions of the planet are quickly becoming uninhabitable
  • Higher temperatures and dryer weather means more Wildfires
  • Higher temperatures means more water evaporates leading to more and bigger Storms
  • Bigger storms lead to more flooding
  • Due to the destruction of habitat and climate change, we are losing species at a rate of 1,000 times faster than the natural rate of extinction - Earth’s Sixth Mass Extinction has begun
    • This is due to more than just climate change but climate change is still a large factor
• In climate science, a tipping point is a critical threshold that, when crossed, leads to large and often irreversible changes in the climate system. If tipping points are crossed they are likely to have sever impacts on human society
  • These tipping points are things that cannot be reversed either
• Global warming is causing glaciers to disappear world-wide
  • Glaciers in Greenland are retreating at a very accelerated pace
• Arctic summer sea ice area has dropped almost in half since the 1980s
  • It could potentially even completely disappear in the next 40 years
  • Arctic sea ice melting increases sea levels by a very small amount
  • Land based ice (Antarctic and Greenland) melting wo0uld increase sea levels by a LOT (60 meters)
• Net Antarctic ice is also being lost at a fast pace, though the distribution of change is not uniform due to changes in air and ocean currents
• The melting of the Thwaites Glacier in Western Antarctica is currently the greatest danger to global sea level rise
• Losing all the ice would not put us all under water
  • We would however lose a LOT of cities and land. We would lose a lot of California, all of Florida and a lot of the Eastern United States coast
  • This wouldn’t happen for hundreds of years, but it definitely could

What is and What is not debatable §

• There is no debate within the scientific community as to whether humans are the primary cause of current climate change
• Greater than 99% of peer-reviewed scientific papers dealing with climate change endorse the position that humans are causing global warming
• Confirmation Bias - the urge to believe only things that confirm, what you already believe to be true
• Backfire Effect - instead of embracing the truth, many believers double down on their beliefs after being presented with evidence that contradicts them
• Effective Tipping Point - “Motivated reasoners” start to accept hard truths after seeing enough claims debunked over and over
• Climate change will inevitably lead to conflict. Changing climates will make places unlivable, forcing people to move, leading to conflict
• Climate disasters are having a large effect on the economy
• The Paris Climate Accord target of below 2 degrees Celsius temperature increase by 2100 will NOT be achieved, and definitely not with current policies
• At least in the U.S. renewable energy has surpassed coal and nuclear energy production for the first time
• However, per person the US continues to generate CO2 at a far faster rate than any other country in the world
• There are some strategies to fight global warming but none of them are likely to work unless we cut greenhouse gas emissions
• One of the best ways for you to reduce emissions is to avoid long flights since they produce such a large amount of emissions
• Reducing your carbon footprint is a good idea, but its really a marketing campaign by companies to make you feel like you’re at fault