Climate Change Research

HOW HAS HUMAN ACTIVITY AFFECTED THE NATURAL CO2 LEVELS?

The harnessing of energy through combustion of coal and oil was central to industrialization and the development of modern transportation systems, but this process emits CO2 and water vapor into the atmosphere. Under natural circumstances, this carbon may have remained in the ground for millions of years. Anthropogenic (originating in human activity) emissions and land use have shifted 19-36% of carbon out of these stores into the atmosphere and ocean. More than half of historic fossil fuel carbon emissions have occurred in the last three decades. 

HOW MUCH ARE CO2 LEVELS EXPECTED TO RISE BY 2100, AND HOW MUCH WOULD THE PLANET WARM AS A RESULT?  

Predicting the future of CO2 levels is difficult inasmuch as the levels will be affected by human behavior over the period measured. Therefore, scientists create models based on different assumptions of fossil fuel use. The International Energy Agency (IEA) estimates that if nothing is done to reduce emissions, the world is on track to increase total CO2 levels by as much as two times the current level over the balance of the century. Models assuming varying efforts to reduce emissions result in lower levels. 

“Climate sensitivity,” or the amount that temperature will increase as CO2 concentrations increase, is also difficult to determine, but the range has been estimated to be enough to result in 1.5-4.5 degrees Celsius of warming. Models that look at warming through the end of the century estimate that the likely upper bound is five degrees, although the worst case would be a warming of eight degrees.

WHAT NATURAL FEEDBACK LOOPS ARE TRIGGERED BY CLIMATE CHANGE?

NASA climate scientists categorize factors affecting climate change into the following categories: forcing, feedbacks, and tipping points. Forcing initially drives climate changes and includes solar irradiance and GHG emissions. The second category is climate feedbacks, which are defined as processes that can either amplify (positive feedbacks) or diminish (negative feedbacks) the effects of climate forcings. While forcings may lead to some amount of warming by themselves, it is the feedbacks that accelerate the warming process.

Oceans and ice: A surface’s ability to reflect solar energy is known as “albedo,” and varies between 0 (absorbs all energy) and 1 (reflects all energy). (The loss of ice—which due to its light color has an albedo of 0.5 to 0.7—is a positive feedback. The darker ocean, with an albedo of only 0.06, absorbs much more solar energy, therefore causing more melting of ice and continued warming. This is considered a “very strong” positive feedback. Sea ice with snow is even better and can have an albedo of up to .9, reflecting up to 90% of incoming solar radiation, and insulating the ice. 

Water vapor: Water vapor is one of the strongest climate feedbacks. As the planet warms, the atmosphere holds more water vapor. The increased water vapor in the atmosphere can more than double the direct warming from CO2 in a positive feedback. Clouds from increased water vapor can both increase reflected solar energy in a negative feedback, or trap heat in the atmosphere in a positive feedback, depending on the location and type of clouds.

Methane: Methane is another GHG positive feedback. Because it is stored in frozen peat bogs, permafrost, and other stocks under the sea floor, increasing temperatures that thaw these stores also release the trapped methane into the air, causing amplified warming. 

The existence of these feedbacks adds momentum to even small amounts of warming, making climate change challenging to predict. Even more challenging to predict or measure is the potential for these natural systems to become “tipping points,” which can move the Earth’s climate between drastically different stable states. Both ice loss (in the Arctic, Greenland, and west Antarctic) and mass release of methane could become tipping points.

HOW DO RISING TEMPERATURES AFFECT OUR WEATHER SYSTEMS?

The effect of this “global warming” is not, as the name may misleadingly imply, simply warmer temperatures. In fact, higher global temperatures make the atmosphere more energetic, contributing to increased intensity in weather fluctuations and decreased predictability of weather events. This increased intensity and decreased predictability can be found across our entire climate system, from wind, clouds, and storms to heat waves and more.  

As an example, warming air boosts evaporation and increases water vapor in the atmosphere. This can worsen the length and severity of droughts while at the same time leading to heavier, more dangerous rain and snowstorms. 

Extreme weather events are classified as such if they are unlike 90-95% of similar weather events in the same area. Scientists are learning to estimate how increased GHGs can make an event more severe or more likely to happen, a process referred to as “extreme event attribution.” 

WHAT ARE SOME OBSERVABLE EFFECTS OF CLIMATE CHANGE?

Extreme global temperatures  

• The planet’s average surface temperature has risen about two degrees Fahrenheit since the late 19th century. Most of the warming occurred in the past 35 years, with 16 of the 17 warmest years on record occurring since 2001. 2016 was the warmest year on record; eight of the 12 months were the warmest on record for those respective months.  

• In 1950, record lows and record high temperatures over the course of the year were equal. Over the last decade, record high temperatures happened twice as often as record low temperatures.

Many of the deadliest heat waves in recorded history have happened since 2000. Heat fatalities in the period 2000-2010 were up more than 2,000% compared to the previous decade, according to the World Meteorological Organization. Heat waves are one of the deadliest kinds of natural disaster in the US and kill more people in cities annually than hurricanes, lightning, tornadoes, and floods combined.  

• In North Africa and the Middle East­—home to over a half billion people—the average annual number of extreme high temperature days has doubled since the 1970s.  

• Hundreds of millions of people earn their livelihoods working outside, and billions more depend on goods and services that result from that labor. In high temperatures the human body expels heat by dilating blood vessels and increasing blood flow to the skin to release heat, while sweating cools the skin. At temperatures higher than the body, blood at the skin will not release heat, and at high humidity sweat cannot evaporate and the skin will not cool. As a result, heat exhaustion and heatstroke can occur, triggering seizures and convulsions, and can even be fatal without treatment. Even in less-than-fatal temperatures, working hours and productivity can drop. 

 Oceans and sea level rise

• The oceans have absorbed much of the world’s increased heat, with the top 700 meters of ocean showing warming of 0.302 degrees Fahrenheit since 1969.

• Glacial melt as a result of this warming has raised global sea levels by about eight inches in the last century. The rate in the last two decades, however, is nearly double that of the last century. 

• The Greenland and Antarctic ice sheets have decreased in mass: Data from NASA's Gravity Recovery and Climate Experiment indicate that Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005. 

• Increasing uptake of carbon dioxide by the oceans by 2 billion tons per year has caused the acidity of surface ocean waters to increase by about 30% since the industrial revolution, reducing carbonate in the water that marine organisms such as coral and plankton use to build their shells and skeletons. Additionally, acidic water causes their shells to dissolve and damages corals, which provide habitat for millions of species. 

• The Great Barrier Reef, the world’s largest single structure made by living organisms and a World Heritage Site, is bleaching at an alarming rate. As of 2016, 30% of the corals had died. The Great Barrier Reef Marine Park Authority (GBRMPA), which compiles a report on the reef every five years, most recently rated the status of the reef as “very poor,” and stated that was “largely driven by climate change.” By the end of 2017, 50% of the corals were dead along with two-thirds of the entire reef.  

• A 2019 NOAA study identified 40 different US locations facing accelerating high tide flooding trends. Miami, FL, a city especially vulnerable to flooding due to its construction on top of porous limestone and its location just above sea level, is forecast to spend $400 million to defend its stormwater systems over the next 20 years. 

Additionally, the Army Corps of Engineers is currently considering a multi-billion-dollar plan to build a 10-foot sea wall by the Florida east coast. 

Many of these solutions will prove to be short term in nature. After Hurricane Katrina, the Army Corps of Engineers invested $14 billion to construct levees and floodwalls in New Orleans, a project only expected to provide sufficient protection for another four years.

• In NYC, an estimated $4 billion in property value will be subject to tidal inundation by 2100, as well as other coastal areas. 

• The Rhode Island Coastal Resource Management Council estimated that sea level rise would flood 605 buildings six times a year. Efforts to build sea walls or move structures are only temporary solutions. Also in Rhode Island, the warmer water has plummeted the lobster catch by 75% in the past twenty years.  

• Mumbai, India—the financial capital of the country, with a population of more than 20 million people—has by some estimations the largest concentration of people at risk from sea level rise. The rise, paired with increasingly extreme weather events, threatens the entire city.  

Extreme weather events

• The intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5), have all increased since the early 1980s. 

• NOAA has concluded that on a global scale, there will be an increase in tropical cyclone precipitation rates, cyclone intensity, and frequency of “very intense” tropical cyclones. 

• While average annual precipitation has not changed, India’s Meteorological Department has confirmed that the seasonal reliability of the annual monsoons has increasingly changed to periods of drought followed by intense precipitation and floods. As a result, while Mumbai flooded for weeks at a time in 2019, reservoirs supplying drinking water to the southern city of Chennai dried out.

• In 2018, the southern coastal state of Kerala, one of the most densely populated in India, experienced the worst floods in almost 100 years, affecting an estimated 5.4 million people. Between June 1 and August 28, cumulative rainfall was more than 42% higher than typical averages. 

• Wildfires in California have increased fivefold since 1972—a result of outdated electrical utility equipment and hot, dry, and windy conditions. Increasingly fluctuating temperatures reduce the lifespan of asphalt, add stress to expansion joints on bridges, and cause bucking of railways, among other effects.  

Economic impact 

• Across the US, insurance premiums are rising in areas vulnerable to changing climate, and certain areas are uninsurable. In California, where wildfires are increasingly frequent and damaging, the state banned insurance companies from dropping policies of customers in or near recent fire-affected areas. California insurers filed for 80 rate increases in 2018, more than double that of 2015.   

• By 2030, global fish demand is expected to increase by 20% or more, while “fish populations in the oceans are being depleted due to destructive fishing practices, inadequate policies and climate change.” Fish is the primary source of protein or income for more than three billion people globally.

• The Australian Great Barrier Reef, one of the most biologically diverse places in the world, which has suffered severe bleaching (as described above), supports 64,000 jobs and contributes $6.4 billion annually to Australia’s economy.

WHAT IS THE CURRENT GOAL FOR STEMMING CLIMATE CHANGE? 

The most ubiquitous global climate change goal was set at the Paris Accord on climate change, which set the goal of limiting the global temperature increase to below two degrees Celsius, while pursuing efforts to limit the increase to 1.5 degrees. Currently, 197 states and the European Union have signed this agreement with “a collective aim to strengthen the global response to the threat of climate change by keeping a global temperature rise this century well below two degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius.” Eight signatories have not backed the deal, including large oil-exporting nations such as Turkey.

Specifically, the agreement does the following: 

• Sets the goal of limiting global temperature increase to below two degrees Celsius, while pursuing efforts to limit the increase to 1.5 degrees. 

• Establishes the concept of Global Peaking, which means that no country that is a party to the agreement should see their CO2 emissions increase after signing the agreement. 

• Commits all parties to prepare, communicate, and maintain a nationally determined contribution (NDC) and to pursue domestic measures to achieve it. Parties must communicate their progress on achieving their goals every five years. 

• Encourages countries to improve “sinks and reservoirs.” These are places like forests and large waterways that help to absorb harmful emissions. 

• Develops a framework for cooperation between parties. This section is about opening the market so things like renewable energy tech and companies can easily cross borders.  

• Creates a fund to help developing countries deal with losses associated with climate change (hurricanes, rising sea levels, etc.).  

• Provides finance, technology, and capacity-building support for developing nations. 

• Creates financing of a public awareness campaign on the dangers of climate change. 

• Requires all parties to be transparent in regards to their emission levels.  

• Provides that a “global stocktake” will take place in 2023 and every five years thereafter, to assess collective progress toward meeting the goals of the agreement.  

WHY 1.5 DEGREES?

The Brookings Institute provides a brief history of this goal. “The origins are in the original international treaty on climate change, the 1992 Framework Convention on Climate Change. This treaty (which was negotiated under the George H.W. Bush administration), recognized the importance of climate change and set up a process for the international community to begin to address it. The core principle of the international approach to climate, formally embedded in that agreement, was ‘to avoid dangerous anthropogenic interference in the climate system.’”

“Consensus was built around the two-degree goal but there were concerns that even two degrees was too high. This led to the embedding of a 1.5 degree goal at the beginning of the landmark 2015 Paris Agreement: ‘Holding the increase in the global average temperature to well below two degrees above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees above pre-industrial levels.’”

The Intergovernmental Panel on Climate Change (IPCC) provides the following estimates of the impact and risk associated with the various degrees of warming below and above 1.5.