1. Carbon dioxide (CO2), methane, and nitrous oxides are greenhouse gases: they trap some of the Earth’s heat, which keeps the planet warm enough for life to survive. The concentrations of these gases are increasing in the atmosphere, with the concentration of CO2 having increased 30% since 1900. Ice core records show that the current rate of CO2 increase and the amount of CO2 in the atmosphere is unprecedented over the last 800,000 years. Rock records reveal that the last time atmospheric CO2 levels were this high was 3 million years ago and sea level was 22 m (72 feet) higher than it is today. We are on track to triple or quadruple CO2 concentrations in the atmosphere by 2100 compared to the year 1900.
2. The source of the added CO2 in the atmosphere is from the combustion of fossil fuels – burning oil, gas, and coal for powering our homes, cars, factories, industries, communications networks, and electrical needs – and from cement production. Animal husbandry, rice production, and fossil fuel combustion have all contributed to the increases in methane.
3. As atmospheric CO2 and other greenhouse gases have increased, global temperatures also have increased. Over the past century, global average temperatures have increased by almost 1.8⁰F (1⁰C). We are currently on track for the planet to warm by another 7.2⁰F (4⁰C) by 2100, but with Polar regions warming by up to 18⁰F (10⁰C). To put this in perspective, the global average temperature difference between an ice age and a non-ice age is about 7.2⁰F (4⁰C). In Central Ohio, temperatures from 1951 to 2012 increased by 2.3⁰F (1.3⁰C), which is faster than the national and global rates.
4. Atmospheric CO2 dissolves in the surface ocean, reacts with the seawater, and makes the oceans more acidic. This is called ocean acidification. Over the past century, our oceans have become 30% more acidic. By 2100, the oceans will become another 100-150% more acidic.
5. Sea level has risen by 8 in (20cm) over the last century due to warming of the ocean which causes the water to expand, and due to the melting of Earth’s natural ice reservoirs. We are on track for sea levels to rise by another 30 in (75cm) by the end of this century.
6. Sea ice and glaciers are melting due to global warming, and snow cover is declining. The Arctic Ocean is expected to be free of ice during the summer by 2030, many mountain glaciers will disappear within the next decade, and many areas have seen a shift from snowfall to rainfall.
1. Sea level rise is already starting to strain infrastructure protecting coastal property from storms and flooding, and will overwhelm low-lying nations soon. This will lead to the potential for mass migration of people inland as large areas of coastline become uninhabitable globally. Particularly vulnerable are places like Bangladesh, low-lying island nations, and southern Louisiana and Florida.
2. Severe weather events have increased over the past decades. Increases in the number of severe heat waves has resulted in human deaths and huge economic losses. Increases in the number of severe storms in some regions and increasingly severe droughts in other regions will continue over this century. This will change where crops can be grown, with many countries predicted to suffer significant decreases in crop yields leading to potential social upheaval. It will also increase the probability of severe rainfall hazards like flooding and landslides. In Central Ohio, the number of days with 1.25 in (3.2 cm) of rain, an amount that produces nuisance flooding, has increased by 78% since1951. Also in Ohio, climate change will lower grain yield and field viability, and increase the need for cooling and water for livestock.
3. Melting of mountain glaciers will reduce the amount of freshwater available for half of humanity. Shifts in snow and snowmelt is putting stress on infrastructure like dams and reservoirs, and is having economic effects on agriculture, hydropower generation, and winter recreation industries.
4. Plants and animals will respond differently to rapid rates of warming. Many species, such as polar bears and arctic fox who depend on snow and ice for survival, will lose their habitat and be threatened with extinction. Others, such as some tropical mosquitoes that carry diseases like malaria and zika, will be able to migrate into more temperate zones, increasing the range over which diseases spread.
5. Ocean acidity interferes with the formation of shells and bones in marine organisms and can severely affect their health and survival. Decreases in the shelled plankton at the base of the food chain will result in declining fish stocks.
6. The double stress of seawater warming and ocean acidification threatens ecosystems like coral reefs. Coral reefs house 33% of all marine species. Yet huge die-offs caused by warmer oceans have been recorded more frequently over the past few years. Loss of reefs would further lead to mass human migration and economic destabilization of tropical developing countries where a significant portion of the annual GDP depends on coral reef goods and services like fisheries and tourism.
7. Declines in food security, drinking water security, environmental security, and infrastructure security have great potential to adversely affect quality of life around the world. Vulnerable populations, both those alive today and in future generations, who have contributed little if anything to climate change will be most negatively impacted. This could result in social upheaval and humanitarian crises.
1. Reduce CO2 and other greenhouse gas emissions. Though warming is now inevitable, the degree of warming can still be minimized and the rate of warming can be dramatically slowed by changing how we source and consume our energy. If greenhouse gas emissions start to slow by 2020, we would reduce the average warming on the planet by threefold. This will give humans more time to innovate technologies to deal with climate change problems, and will minimize or slow the disruption to food crops, the number of people who will be climate change refugees, and the spread of tropical diseases.
2. There are no other viable solutions at this time but to reduce CO2 and other greenhouse gas emissions. Physically removing CO2 from the air and pumping it into the ground or to the seafloor are economically and logistically not realistic options at this time. Untested geoengineering methods such as solar radiation management have serious risks, making such options unrealistic to be seriously considered.
3. We currently have much of the technology needed to transition to a non-fossil fuel economy. Adoption of energy efficiency and renewable energy technologies coupled with more technological innovation and planning for mass human migration and crop yield changes, will enable us to reduce the amount of greenhouse gases we release in the atmosphere and to minimize the economic, social, and humanitarian disruptions that are occurring because of climate change.