A 2016 study concludes that reducing global greenhouse gas emissions avoids the risk of three feet of global sea level rise by 2100, more than 15 feet by 2200, and over 43 feet by 2500 due to Antarctic ice melting.
If we were to significantly cut down emissions, the Antarctic ice sheet would likely remain stable over time, creating almost no sea level rise by 2100, and under one foot by 2500.
This would prevent the risk of catastrophic flooding in low-lying areas of major U.S. cities such as New York due to sea level rise.
A 2015 study says that if global greenhouse gas emissions are reduced significantly, parts of Southern California (such as Los Angeles and Riverside) can avoid over a month of additional extremely hot (95-degree) days by the end of the century.
Los Angeles, which currently averages 6 extremely hot days per year, will face either 54 (if global emissions continue) or 15 extremely hot days (if global emissions are cut) by 2100.
Takeaway: reliability concerns about the transition to renewable electricity are valid, but not insurmountable.
Potential U.S. Electricity Generation Mix in 2050 (%)
A 2012 analysis shows that the U.S. can achieve over 80% carbon-free electricity generation by 2050, while maintaining grid reliability in every U.S. region and at relatively low cost.
This would reduce power plant greenhouse gas (GHG) emissions by more than three-quarters from current levels (equivalent to reducing overall emissions by about one-quarter).
This would increase the average American's monthly power bill by about $20, but this excludes power bill savings from energy efficiency and healthcare cost savings from reduced pollution.
Takeaway: we need to transition from coal to carbon-free energy, not natural gas, in order to prevent the worst climate impacts.
A 2011 paper finds that if the world converted all coal power plants to natural gas by 2050, the resulting reduction in global temperatures would not be big enough to prevent the worst impacts of climate change.
Even if, optimistically, no natural gas leaked into the atmosphere during its production and distribution, the resulting temperature reduction from a complete coal-to-gas shift would still be too small to prevent the worst impacts of climate change.
Takeaway: while it may be the case that hybrids are better for the climate than electric cars in some places today, electric cars have more potential than hybrids to reduce emissions from oil in the long run.
A 2015 report measured that two-thirds of Americans live in regions (including California, Texas, Florida, New York, New England, and the entire Northwest) where driving an electric vehicle (EV) produces fewer greenhouse gases (GHGs) than the most efficient gas-powered vehicle.
Even in regions where electricity used to charge EVs is the dirtiest, an EV pollutes 21% less than the average new gasoline-powered vehicle.
If the U.S. moved to a grid supplied by 80% renewable energy, an EV would emit roughly 90% less GHG pollution than the current average new gasoline-powered vehicle.
Citibank estimates that global damages from doing nothing to reduce greenhouse gas (GHG) emissions range from $5 to $44 trillion of net present value (global GDP is currently $80 trillion), noting that these estimates likely undercount the true value of total damages.
The study estimates that the cost of investments to reduce GHG emissions range from $2 to $5 trillion of net present value.
The study also shows that the return on investment in reducing GHG emissions ranges from between 3% and 10% by 2040.
An EPA study estimates that a significant global reduction in greenhouse gas (GHG) emissions can avoid at least $235 billion in annual damages in the U.S. by 2050.
The biggest benefit comes from public health improvements ($200 billion annually) such as improved air and water quality, fewer heat-related deaths, and increased labor productivity.
By 2100, EPA estimates global GHG reduction could result in at least $1.2 trillion in annual avoided damages in the U.S., mostly from improved air quality.
Takeaway: the majority of emissions reductions expected by 2030, relative to 2005, are expected to happen regardless of whether the Clean Power Plan exists.
Relative to the Clean Power Plan's greenhouse gas (GHG) reduction goals for power plants in 2030 (32% below 2005 levels), the U.S. is already two-thirds of the way there (21% below 2005 levels).
Without the Clean Power Plan (CPP), the Department of Energy projects power plant GHG emissions will stay roughly constant, at 20% below 2005 levels in 2030.
Thus, the CPP is the difference between emissions staying constant and declining slightly.
Takeaway: the world must treat the 2 degree target as an upper bound in order to minimize climate risk.
A 2013 study finds that levels of greenhouse gas emissions previously thought to be consistent with limiting global temperature increase to 2 degrees (regarded by some as a manageable level of warming) risk triggering secondary effects that, in the long term, would result in 3 or 4 degrees of warming.
3 or 4 degrees of warming would have major undesirable consequences such as flooded coastal cities and displaced populations.
If no further action is taken, the world is projected to exceed 2 degrees of warming before 2100.
Global Contribution of Each Technology to a Safe Emissions Level (%)
2016 data show the potential roles of different technologies to bend global emissions down from their current trajectory to levels consistent with a 2-degree level of warming.
The data show that energy efficiency is the biggest solution, accounting for roughly one-third of necessary emissions reductions.
In the U.S. energy efficiency provides nearly 40% of the solution.