The Earth’s Climate is Changing

Written by IWF Board Member – Coralie Palmer

The Earth’s climate is changing. Global land and ocean temperatures have increased, the
cryosphere has diminished, sea levels have risen and the oceans have become more acidic.
Recent anthropogenic emissions of greenhouse gases are the highest in history and the evidence that recent climate change has been driven primarily by human actions is overwhelmingly strong and widely accepted by the scientific community [1, 2, 3, 4]. Impacts of climate change on food security, health, biodiversity, ecosystem services, infrastructure and economic development are already being felt; as rates and magnitudes of warming, sea level rise and ocean acidification increase, ecosystems and human populations will face increased and unprecedented risks [1, 5, 6]

The Earth’s Atmosphere and Oceans are Warming. 
Since 1901, almost the entire world has experienced surface warming [1]. From 1900 to 1980 a
new temperature record was set on average every 13.5 years; since 1981 it has increased to every 3 years [7]. 2017 was the 41st consecutive year with global land and ocean temperatures above the 20th century average, with the six warmest years on record occurring since 2010 [7]. The 2017 average global temperature across land and ocean surface areas was 1.51°F above the 20th century average; for March 2017 it was 1.9°F above average – marking the first time the monthly temperature departure from average surpassed 1.8°F in the absence of an El Niño episode [7]. For the third consecutive year every state across the contiguous U.S. and Alaska had an aboveaverage annual temperature in 2017; five states – Arizona, Georgia, New Mexico, North Carolina and South Carolina – had their warmest year on record [8]. For November 2017, Barrow, AK had a temperature departure of 16.4°F above average [7]. The average global temperature for January–July 2018 was the fourth highest on record, and 2018 is gearing up to end up among the top five warmest years [9].

One of the primary impacts of these increases has been to alter the global water cycle. The ocean plays a vital role in climate moderation; ocean warming dominates the increase in energy in the climate system, accounting for more than 90% of the energy accumulated between 1970 and 2010 [1, 10]. Increased water vapor in the atmosphere is a potent greenhouse gas (GHG); warmer air can hold more water vapor, creating an amplifying feedback loop [11]. Warming has led to glaciers and sea and freshwater ice melting at an accelerated pace, exposing dark ocean waters which absorb more sunlight, triggering another feedback loop [12].

Arctic sea ice extent has decreased in every season and every successive decade since 1979 by 3.5-4.1% per decade; on March 7th, 2017, the Arctic sea ice extent reached its yearly maximum extent at 5.57 million square miles, the smallest annual maximum extent on record, 471,000 square miles below average [1, 13]. The Antarctic sea ice reached its smallest minimum extent on record on March 3rd, 2017 at 815,000 square miles [13]. Permafrost has reduced in most northern hemisphere regions since the 1980s [1].

Ocean thermal expansion, melting of glaciers and the ice sheets and changes in land water
storage have contributed to a rise in sea level [11,12]. Global mean sea level has risen by about
0.16–0.21m since 1900, with a rate since the mid 19th century greater than during the previous
2000 years and an approximate rise of 0.07m occurring since 1993 [1, 11, 14]. In 2018, high tide
flood frequencies are predicted to be 60% higher across U.S. coastlines as compared to
frequencies typical in 2000, due primarily to local sea level rise [15]. The ocean has absorbed
about 30% of emitted anthropogenic carbon dioxide (CO2) resulting in ocean acidification, with
a 26% increase in acidity since the beginning of the industrial era [1]. Both coastal and oceanic
oxygen concentrations have decreased, while regional changes in salinity provide evidence of
changes in evaporation and precipitation [1, 10] .

Anthropogenic Drivers of Climate Change – Increased CO2 and Greenhouse Gases.
Processes and substances that alter the Earth’s energy budget are driving climate change [1].
There is overwhelming scientific agreement that recent global warming is primarily due to
human activities – there is 97% consensus in published climate research and the National
Academies of Science from 80 countries have issued statements endorsing the consensus
position [2, 3, 4, 5, 11].

Detailed analyses have shown that warming over the past four decades is mainly a result of the
increased concentration of CO2 and other GHGs, which absorb infrared radiation emitted from the Earth’s surface [11]. Emissions have driven atmospheric concentrations of CO2, methane (CH4) and nitrous oxide (N2O) to levels unprecedented in at least the last 800,000 years, leading to an uptake of energy by the climate system [1]. CO2 is the major anthropogenic GHG [1]. Atmospheric CO2 levels have varied from 180-300 ppm; in 2013, CO2 levels surpassed 400 ppm for the first time in recorded history, 40% more than the highest natural levels over the past 800,000 years; in July 2018, the level was measured at 408 ppm [11, 12, 16]. Approximately half of the cumulative anthropogenic CO2 emissions between 1750 and 2011 have occurred in the last 40 years [1].

CO2 emissions from fossil fuel combustion and industrial processes have been the greatest
contributor to GHG emissions, accounting for about 78% of the 1970-2010 increase, driven
primarily by economic and population growth [1]. Deforestation and other land use changes have
also released carbon from the biosphere [11]. Since 1970, cumulative CO2 emissions from fossil
fuel combustion, cement production and flaring have tripled; cumulative CO2 emissions from
forestry and other land use have increased by about 40% [1].

Evidence that recent climate change is caused largely by anthropogenic factors comes from
climate simulation models, fingerprinting patterns of climate change and an understanding of
physics [11]. Measuring the isotopic fingerprint of atmospheric CO2 reveals that recent increases
are due largely to human actions, primarily fossil fuel combustion – carbon from fossil fuels has
no 14C and is depleted in 13C compared to living systems [11, 12]. Climate model predictions of
surface warming, atmospheric temperature and moisture, ocean heat content, sea level rise and
loss of land and sea ice are consistent with observed changes only when the models include
anthropogenic influences [11]. The troposphere has warmed and the lower stratosphere cooled
since the mid-20th century [1]. This pattern is consistent with predictions from models indicating
that anthropogenic increases in CO2 would lead to tropospheric warming and stratospheric
cooling, while increases in the Sun’s output would warm the troposphere and full vertical extent
of the stratosphere [11]. Direct satellite measurements since the late 1970s show no net increase
in the Sun’s output, while global surface temperatures have increased [11].

The Impacts of Inaction
Impacts of climate change on food security, health, biodiversity, ecosystem services,
infrastructure and economic development are already being felt, particularly in developing
countries [5, 6]. Terrestrial, freshwater and marine species have displayed altered ranges,
migration patterns, abundances and trophic interactions [1, 11]. Surface temperatures are projected to rise over the 21st century; it is predicted that heat waves will be more frequent; extreme precipitation events, storms and flooding will become more intense and frequent; freshwater supplies will change and wildfires and droughts intensify [1, 4, 11, 12]. Ocean acidification, warming and deoxygenation present multiple stressors for marine ecosystems, affecting biodiversity and fisheries and influencing storm systems and climatic feedback loops [10]. Acidification has been shown to impact corals and and other marine organisms, threatening their ability to form skeletal structures [17]. Additionally, acidification alters nutrient cycling, affecting ecosystem dynamics [11]. Climate change impacts are projected to slow economic growth, disproportionately affecting the most disadvantaged and representing a threat to equitable and sustainable development [1]. Many of the socio-economic impacts will be borne by developing nations, and many of the world’s most vulnerable people may be displaced [1].

If emissions continue on their present trajectory, warming of 4.7 to 8.6 °F is expected by the end
of the 21st century [5, 11]. Calculations are complicated by feedback chains, with models
indicating they will amplify warming by a factor of 1.5-4.5 [11]. As the magnitude of warming
increases, so does the likelihood of increasingly severe impacts. Without additional mitigation,
warming by the end of the 21st century will lead to very high risks of widespread and
irreversible impacts; delaying mitigation measures will increase the costs and challenges of
limiting warming and raises the risks [1, 5].

Stemming the Increase in Global CO2
Reducing CO2 emissions will reduce climate risks and contribute to equitable and sustainable
development. Increased use of renewable energy; increased energy efficiency; improvements in
the urban environment and transport; increased carbon capture, use and storage and
improvements in land use are all key to stemming the increase in CO2 emissions [5].

Transitioning to a lower-carbon economy will require significant investment, requiring international and national public finance and private sector involvement; the economic benefits of such investment will be substantial [6]. Finance to support low-carbon investment is growing; climate change considerations are increasingly being integrated into business strategies while the social and economic costs of a fossil-fuel based economy are becoming clearer [6]. Technological innovation, economic trends and global political commitment are building momentum for change; there are multiple benefits associated with climate action and clear links to economic growth and sustainable development [5, 6]. However, action is not at the scale or speed needed [6].

Barriers include lack of legal and regulatory frameworks, existence of inefficient subsidies, lack
of carbon pricing and inadequate finance for new technologies, infrastructure and innovation [5].
Overcoming these barriers to CO2 emission reduction will require an integrated suite of policies,
regulations, investment shifts and innovations and a high level of cooperation at international,
regional and national levels [1, 5]. Cooperation between national governments, the private sector, civil society and multilateral organizations will be critical; technology transfer and financial and capacity building support for developing countries will be key [5, 6].

The Paris Climate Conference (COP21) in December 2015, provided a vital foundation
for building a lower-carbon global economy [6]. To date, 195 Parties have signed and 180 Parties
ratified the first universal, legally binding global climate deal which it is hoped will act as a
bridge between today’s policies and climate-neutrality by the end of the century [18, 19]. On
August 4th, 2017, the United States officially notified the United Nations that it intends to
withdraw from the agreement [20].

Climate Change in Indiana
According to a recent report published by Purdue University, Indiana has warmed by 1.2°F since
1895; temperatures are projected to rise approximately 5°F to 6°F by mid-century and
significantly more by the end of the century [21]. These changes are predicted to increase the
chance of extreme heat and reduce the chance of extreme cold, and to alter the timing and length
of the frost-free growing season. Associated impacts on air quality and health – including
impacts linked to allergies, extreme heat and changes in disease-carrying insect populations – and implications for crops and invasive species are key concerns [21, 22]. The annual number of deaths related to temperature and worsening air quality in Indiana is expected to increase [22]. Average annual precipitation in Indiana has increased by 5.6 inches since 1895, and more rain is falling as heavy downpours; predicted increased precipitation for spring and winter raises concerns around increased flood risks, including water pollution from overflowing sewer systems and fertilizer run off, and health impacts associated with increased exposure to waterborne disease, harmful algal blooms and mold [21, 22]. Predicted changes for summer and fall precipitation are less certain, however warmer summers with the same or reduced rainfall may increase stress on drinking water supplies and crops [21].

Rising temperatures and altered precipitation across the Midwest will likely have widespread
consequences for Indiana’s forests, including shifts in the distributions and abundances
of trees and understory plants, and is expected to increase the risk of damage to urban forests,
prairies, farms and other green spaces [23, 24]. Changes in forest composition have the potential to decrease forest productivity and carbon uptake, while predicted changes in precipitation may promote pathogen related diseases and damage seedlings at sensitive periods of growth [23]. Warmer temperatures may increase the number of invasive plant species in Indiana, with plants such as kudzu and Chinese privet predicted to expand their ranges northward [23]. These changes have worrying implications for many of Indiana’s fragile native plant populations and the wildlife that depends on them. Shifts in forest and understory plant composition will strongly
influence Indiana’s wildlife populations, while phenological shifts associated with climate change are predicted to affect migratory wildlife.

Recent studies highlight that proactive efforts to restore areas with climate-adapted species may
ensure the greatest long-term benefits for Indiana’s wildlife, while the importance of maintaining
urban green infrastructure to support economic, environmental and health benefits to cities in
Indiana will likely increase in our changing climate [23, 24].

We are excited to welcome members of the Purdue Climate Change Research Center for their
presentation at our offices on August 30th, 2018. If you might be interested to find out more
about the latest on Indiana-specific climate impacts, please join us …………

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