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Freshly Baked Science

Climate Change: The Sign Read, 'Nobody Minds If You Miss School on a Dead Planet'.

by Bruce Krawisz

Emeritus Researcher at Marshfield Clinic Research Institute

6th June 2019

We may feel anxiety and sadness when we hear about or experience climate change, ecosystem destruction, or species extinction.  Despite these painful feelings, it is essential to understand and discuss climate change in order to make reasonable decisions about the future of the planet. 


Climate change is a very important topic for younger generations as they will suffer its consequences.  Reducing your impact on the planet by living a lifestyle with a small ecological footprint makes a difference to everyone’s lives and choosing a career that helps to reduce climate change is even better.  Making good life choices starts with understanding scientific information about the climate and the environment.

Science of Climate Change

The sun emits visible and ultraviolet light.  Some of this light is reflected by ice and clouds, back to space; the remainder provides light and heat to warm the Earth.  Because the average temperature of the Earth is much warmer than outer space (16°C compared to -273°C), some of the heat from Earth travels through the atmosphere to outer space.  The amount of heat lost is influenced by the atmosphere which can capture and retain heat before it leaves for outer space.  The climate is a balance between energy received from the sun, energy reflected back by ice and clouds, and the amount of heat retained by the atmosphere.  When extra heat is added to the ecosystem, the average temperature of Earth increases.

The atmosphere functions like insulation on a house or like a blanket around you.  It reduces heat loss by slowing the movement of heat from Earth to space. Earth is our home, outer space is the cold exterior, and the atmosphere is the insulation of our home.  This retention of heat is called the greenhouse effect. The greenhouse effect is not new; greenhouse gases have warmed our atmosphere for about 4 billion years.

A greenhouse gas molecule can absorb a unit of heat energy (called a photon) and temporarily retain it in its molecular structure. There are currently four major greenhouse gases in our atmosphere: water (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).  Without these greenhouse gases, the temperature of the Earth’s surface might be as much as 33°C cooler.  During almost all of planetary history, greenhouse gases have benefited life on Earth by providing additional warmth. 

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Sadly, human activities have greatly increased the amounts of greenhouse gases in the atmosphere. Burning fossil fuels and cutting down forests has increased CO2 concentrations. Each year human actions release about 35 billion metric tons of CO2 into the atmosphere. We have changed the atmospheric CO2 concentration from about 280 parts per million in 1881 to 412 parts per million today. Human activities have also increased concentrations of CH4 and N2O in the atmosphere.  When we increase greenhouse gas concentrations, more heat is retained in the atmosphere and the climate warms. Human actions have released enough extra greenhouse gases to account for all global warming that occurred since 1950.

Consequences of Anthropogenic Climate Change

The American College of Physicians Health and Public Policy Committee says, “Climate change could have a devastating effect on human and environmental health.”  The atmosphere, lakes, rivers, oceans and the surface of the earth are warming.  The average temperature of the earth has increased by 1.0°C from 1901 – 2016.  Reliable worldwide temperature records go back to 1881 and since 1881, the warmest years have been 2014, 2015, 2016, 2017, and 2018.  There are now more heatwaves and more record-setting elevated temperatures occurring around the world.

Places that have more heat, but do not receive more rain, may develop drought, like in the US southwest.  Human activities raise temperatures causing increased evaporation and transpiration of water which, in turn, causes depletion of moisture in the soil. So, even if rainfall stays the same, hotter temperatures reduce soil moisture. In the Western US, the Colorado and Rio Grande Rivers are shrinking due to the prolonged drought.  Since 1980 there has also been an increase in the size and destructiveness of forest fires in Western United States caused by higher temperatures and longer summer seasons.

As temperatures increase, there is more evaporation of water and, on average, atmospheric humidity increases.  Some of this water travels as clouds until it falls back to earth as rain.  Greater evaporation causes more rainfall in some areas, increasing the risk of floods. It may appear paradoxical that global warming is expected to cause both floods and droughts.  This can be understood by thinking of droughts and floods as local effects.  With more water vapour in the atmosphere, there may be more rain, but this rain will fall only in some areas.   Alternatively, with hotter average temperatures, those places that do not receive greater rainfall, will succumb more quickly to drought.

Hurricanes and tropical storms derive their energy from the heat in ocean water.  These storms evaporate warm water from the ocean, convert the heat energy of the water into wind, and then return cool water as rain.  A hurricane is like a machine that extracts heat and converts it to wind. The more heat available, the more wind a tropical storm can produce.  As human activities warm ocean water, we make warmer water available for hurricanes.  This means that when a hurricane forms, it may be larger and more powerful because it has extra heat.  Hurricane Irma which devastated the US Virgin Islands and Florida in 2017 was a category 5 hurricane for a longer time than any previous hurricane. 

Unfortunately, we can expect hurricanes to become more powerful as warming continues. This does not necessarily mean that there will be more hurricanes.  Rather, it means that when a hurricane forms, there will be additional energy available to the hurricane.  Unusually large or powerful hurricanes like Irma, Maria, Harvey, Florence, and Michael are, in part, a consequence of global warming.

Some human diseases are spread by insects.  Because insects are cold-blooded (poikilothermic), they are sensitive to temperature changes and become more active in warmer weather.  Climate change may alter the geographic and seasonal distributions of these insect vectors and the diseases they carry.  Ticks that carry the bacterium (Borrelia burgdorferi) that causes Lyme disease are expanding northward in Europe and North America.  The number of new cases of Lyme disease has increased in Maine, Pennsylvania, Minnesota, and Canada.  These ticks (black-legged deer ticks) thrive in a warm and humid climate. 


As summers become longer and hotter and winters milder, the time span for tick activity increases.  Most cases of Lyme disease are acquired in the summer when ticks are more active and people are out in natural settings.  Tropical mosquitoes (genus Anopheles and Aedes) that carry chikungunya virus, zikavirus, malaria, and Dengue fever virus are expanding their geographic ranges as the climate warms. 

These insect vectors and the diseases they transmit have complex life cycles.  There are many factors that affect disease transmission to humans.  Global warming may increase the risk of these diseases as these mosquitoes move into new geographic areas.

Farmers in temperate climates such as the American Midwest will face problems caused by climate change.  There will be more heat with more rapid loss of soil moisture and possibly more crop-destroying insects.  Greater heat may directly damage some crops during the summer.  Some plants cannot grow when the average temperature exceeds 35°C for long time periods.  Reduced soil moisture due to increased evapotranspiration is an indirect consequence of higher temperatures.  Higher temperatures also cause increased metabolic rates in cold-blooded insect pests which, alongside warmer summers and milder winters, may allow larger insect pest population sizes.

The earth’s cryosphere (glaciers, polar ice caps, permafrost) is melting.  By 2040 there may be no ice on the Arctic ocean during the summer.  When ice on land melts and water flows into the ocean, sea level rises.  As the ocean water warms, the average distance between water molecules increases and the ocean volume expands.  This is called the thermal expansion of water.  Sea level is rising due to both melting of ice on land and thermal expansion of water. 


About 10% of the world’s human population live on land that is 10 meters or less above sea level.  This includes many of earth’s largest cities (New York, Miami, Jakarta, Shanghai, London).  As sea levels rise from climate change, people will be forced to evacuate coastal areas or construct sea walls to protect them.  Island nations such as Melanesia, Micronesia, and Polynesia face similar fates to low-lying coastal cities.  The young people of some of these islands may be the last generation to live in their homeland.

Clean potable water may become more difficult to obtain.  Floods contaminate clean water sources with manure, bacteria, and industrial chemicals like coal ash.  Rising sea levels may add salt to adjacent freshwater and render these water sources unsuitable for drinking.  Increasing evaporation due to heat may also reduce the volumes of water in lakes and rivers.


In some areas, there may be more water due to heavy rains or sea level rise, but this water may not be clean enough to drink.  Recently, blooms of toxic algae (Cyanobacteria and Karenia brevis) have poisoned water in Lake Erie and in Florida.  Higher water temperatures due to global warming may be a factor promoting toxic algal blooms.

About 25% of the CO2 released by human activities dissolves into ocean water.  This dissolved CO2 reacts with water to form carbonic acid (H2CO3) which causes the ocean to become more acidic.  Adding carbonic acid is like turning the ocean into the carbonated soda water.  Acidity is measured in units called pH; as acidity increases, pH declines.  The world’s oceans have declined by 0.1 pH unit as a result of this extra CO2.


As acidity increases, it may become more difficult for sea organisms to make shells, threatening corals, lobsters, clams and other shell organisms.  Ocean acidity may reduce commercial fishing harvests if it continues.


Ocean Acidity 

Credit: Global Ocean Data Analysis Project (GLODAP) and the World Ocean Atlas

As ocean waters warm, less oxygen (O2) can dissolve in ocean and lake water.  Fish and some other inhabitants of seas and lakes may have difficulty breathing if there is less O2.  Reduced O2 concentrations may be harmful to sea and lake life, as well as commercial fishing.  Warming of water associated with loss of dissolved O2 is a particular problem in freshwater lakes because freshwater organisms have nowhere else to go.  In Montana, United States, cool, formerly pristine trout streams are warming to the extent that native fish may no longer survive.

People who experience floods, hurricanes, wildfires, and other climate-related disasters may become more susceptible to depression, anxiety, post-traumatic stress disorder, and suicidal behaviour. Adaptation is not a choice for the vast majority of the world’s population. Most people will simply suffer the consequences of climate change with little or no ability to respond effectively.  This may generate more mental illness.


In 2017 the US experienced unusually powerful hurricanes and large wildfires. Years later, recovery is still incomplete.  People have abandoned their homes and jobs and do not know if or when they might return. Climate change creates great problems for people, but there is little they can do. This is the psychological burden of climate change.

Global warming increases air pollution when wildfires release soot particles into the air.  In more than half of the Western US states, the largest wildfire on record has occurred since 2000.  Wildfires release fine particles called PM2.5 (particles less than 2.5 micrometres in size) into the air.  In California, Oregon, Idaho, and Washington, the PM2.5 concentration increases during the fire season (June to September).  On some days during fire season, the concentration of PM2.5 exceeds safety recommendations from the US Environmental Protection Agency.  In parts of the Western United States, the number of days in which the safety limit is exceeded has increased during the years 2007- 2016.  PM2.5 pollution increases the risk of heart disease in susceptible persons and also increases asthmatic symptoms in persons with asthma.

So, the increasing temperature isn’t the only problem that comes with global warming it’s all the knock-on effects too. If you are interested in how you can reduce your own impact on the Earth by making small changes, head to www.conserve-energy-future.com for some simple yet effective tips. If we can all make a little change, we can make a big difference.

If you would like to read more, an excellent, recent, and free source is Global Warming of 1.5°C written by scientists from the Intergovernmental Panel on Climate Change.  You can download the book here: http://www.ipcc.ch/report/sr15/