Extreme Weather Conditions and the Impact on Society

Meteorological challenges 3

Extreme weather conditions and the impact on society

November 21st -22nd 2013., KRAŠ auditorium, Zagreb, Croatia

Is global warming a scientific certainty or political liability?

Authors:

Ivana Mesić

Gordana Medunić

Contents

1. INTRODUCTION 3

2. GEOLOGIC RECORDS OF CLIMATE CHANGES 4

2.1. Mesozoic and Cenozoic Eras 5

2.2. Pleistocene and Holocene Epochs 6

3. CLIMATE CHANGE PREDICTIONS VS ACTUAL PREDICTIONS 9

4. SOCIAL AND POLITICAL REPERCUSSIONS OF CLIMATE CHANGES 12

5. CLIMATE CHANGE AND GLOBAL WATER RESOURCES 17

6. ECOLOGICAL EFFECTS OF CLIMATE CHANGE 21

7. RECENT CLIMATE CHANGE AND SPECIES DIVERSITY 23

8. CONCLUSION 26

9. Literature 27

Internet pages: 29

1. INTRODUCTION

It is impossible to be unaware of recent climate changes on Earth. We do not need any specific research to tell us that the Earth is warming because it's happening right in front of us, and that such warming carries with it a risk of serious impacts for humans and the rest of the planet’s ecosystems. Even so, over the past two decades, skeptics of climate change have frequently accused climate scientists of over-interpreting or overreacting to evidence of human impacts on the climate system. Some of them have gone so far as to declare global warming a ‘‘deception’’ and that the motivation for such exaggeration is to gain media attention and funding for research.

Scientists mostly argue and debate about two different causes for climate changes: human activities and how much of the change occurring might be natural.

2. GEOLOGIC RECORDS OF CLIMATE CHANGES

Throughout much of its history, Earth has generally been a warm planet, much warmer than today. For at least 2.5 billion years of Earth history, sedimentary rocks and their fossil record show evidence of these warmer times and also of shorter colder periods (fig 1). The cold periods of Ice Houses (low levels of carbon dioxide) last several tens of millions of years before the planet returns to its more prevalent Hot House ("greenhouse") state (high levels of carbon dioxide). There have been four reasonably well-documented Ice Houses. Ice Houses occurred about 2.5 billion, 700 million, and 300 million years ago, and the last Ice House began 35 million years ago. Ice ages are those periods of time when large areas of the continents were covered with thick glaciers (MacKenzie, 2002).

Figure 1. Global climate change through time (7)

2.1. Mesozoic and Cenozoic Eras

The Mesozoic Era, which followed the Ice House about 300 million years ago, was characterized by high global mean temperatures (fig 2), at times about 8 to 10°C warmer than today, high carbon dioxide levels, and an absence of ice sheets and deserts. This warm, generally moist climate was followed by a general, but somewhat erratic, cooling during the Cenozoic Era (MacKenzie, 2002.).

Figure 2. Evolution of Mesozoic-Cenozoic δ18O values. Grey dots = brachiopod data, red circles = belemnite data, green circles = planktonic foraminifera and black circles = brachiopod data (Price et al., 2013).

The Paleocene-early Eocene was relatively warm. Temperatures began falling gradually in the mid-Eocene, then fell sharply about 35 million years ago at the Eocene-Oligocene boundary. This event marks the beginning of the last ice House. Since that time, the overall climate of Earth has continued to cool erratically. Currently the average surface temperature of Earth is about 15°C.

2.2. Pleistocene and Holocene Epochs

The cold periods within the Pleistocene are glacial stages and are times of advance of continental glaciers, falling sea level, and low atmospheric carbon dioxide concentration. Interglacial stages are periods between glacial stages, when the ice retreated from the continents, the climate was warmer, and atmospheric carbon dioxide and sea level were higher. The planet is currently in an interglacial stage, the Holocene Epoch (MacKenzie, 2002).

Major glacial stages are longer in duration than interglacials. Over the last million years, there have been approximately ten major and 40 minor periods of these glacial cold cycles, interspersed with warmer interglacial times. One of the warmer interglacials (named Riss-Würm in Europe and Sangamon in North America), the "Eemian" (fig 3), peaked about 125,000 years ago. In the Eemian, the climate was warmer and more humid than today. Atmospheric carbon dioxide and methane concentrations were higher than during glacial stages, reaching levels of 300 ppmv and 700 ppbv, respectively. The average temperature was 1 to 2°C warmer than that of today. Lions and elephants roamed the land of Cornwall, England. Sea level was higher than today because of less ice locked up in the cryosphere.

Figure 3. Global temperature (left scale) and GHG forcing (right scale) due to CO2, CH4 and N2O from the Vostok ice core (10).

At the end of the Pleistocene Epoch, the climate entered a warming trend. Earth was entering modern times, the Holocene Epoch. The warming trend since the climax of the last glacial stage has not been continuous and has been interrupted by several cool intervals.

One of particular intensity was the Younger Dryas event (fig 4), a 1300-year cold period that began a few thousand years after the climax of the last ice age. Extremely sudden shifts of climate occurred at the beginning and end of the Younger Dryas (MacKenzie, 2002).

Global average temperatures plummeted at least 2 to 3°C, and snow accumulation rates in Greenland decreased by a factor of two. This cooling may have been brought about by a slowing down of the conveyor belt circulation of the ocean and less transport of heat to high northern latitudes of the North Atlantic.

The average surface temperature fe1l 4000 years ago, only to increase again during the Medieval period. This warming trend ended approximately 500 to 600 years ago.

Figure 4. Temperature and snow accumulation during the Holocene and Younger Dryas event (Alley, R.B., 2000).

The Little Ice Age (fig 4) began near the end of the Medieval warm period. Earth experienced a series of temperature variations during this cooling trend. Mountain glaciers reached their fullest extent during the early seventeenth to nineteenth centuries. During the Little lce Age, global mean temperatures were nearly 0.5°C lower than those of the latter part of the nineteenth century. From the middle of the nineteenth century to the present day, the planet has been experiencing a general warming, with minor reversals of temperatures including the period from about 1940 to the mid-1970s.

Broadly speaking, for the last 18,000 years, the global climate warmed several degrees, and sea level rose about 120 meters. Atmospheric carbon dioxide concentrations climbed from 180 to 280 ppm (table 1). Atmospheric methane concentration rose 350 ppb and nitrous oxide concentration 90 ppb. In 2012, the concentration of atmospheric carbon dioxide was about 393.1 ppm, that of methane was 1.81 ppm, and that of nitrous oxide was 0.32 ppm. These increases are due mainly to fossil fuel and biomass burning and agricultural and industrial activities of human society (13).

Table 1. Greenhouse gases – concentration changes and lifetimes. GWP values are given for the estimated relative direct and indirect effects over a 100–yr period (13).

3. CLIMATE CHANGE PREDICTIONS VS ACTUAL PREDICTIONS

Since the release of the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), the claims of over-interpreting to evidence of human impacts on the climate system have become more frequent. However, given the scientific projections regarding the likely outcomes of increased atmospheric concentrations of greenhouse gases since the late 1980s, it is possible to evaluate claims of exaggeration and alarmism (Brysse et al., 2013).

Scientists struggle with projections of global mean surface temperature and other climate attributes that could be expected due to global warming. The most important question is „what confidence can be placed in these projected changes“. We need countable data, comparison of past and recent climate changes to understand and predict future changes (Schwartz et al., 2007).

According to Brysse and colleagues; „scientists are biased not toward alarmism but rather the reverse: toward cautious estimates“. In a 2012 article, Brysse and colleagues gathered available scientific evidence and recent studies showing underpredicted increase of atmospheric greenhouse gases due to global warming.

Comparing actual sea level rising with former IPCC projections, their estimates are obviously not exaggerated. In the TAR, released in 2001, the IPCC predicted an average sea level rise of less than 2 mm/yr, but from 1993 to 2006, sea level actually rose 3.3 mm/yr—more than 50% above the IPCC prediction (Houghton et al., 2001). In a 2008 paper, Roger Pielke, Jr., observed that for sea level rise, actual changes have been greater than forecast in two of three prior IPCC reports. Therefore, previous analysis shows that IPCC projections are biased toward underestimation. These conclusions are also supported by the results of a three year study by the Committee on Strategic Advice on the U.S. Climate Change Science Program (NRC, 2009). This committee found that IPCC projections may have been too conservative in projecting sea level rise, increases in surface temperatures and CO2 emissions by various countries.

The Copenhagen Diagnosis (Allison et al., 2009), like the NRC Report, found that key changes were happening either at the same rate as, or more quickly than anticipated.

Among the key findings are:

-  global temperature increases over the past 25 years have been consistent with model predictions (0.19 ºC per decade),

-  sea level rise has exceeded IPCC predictions by 80%,

-  scientists' worst-case scenario considering CO2 emissions has been realized.

2001 IPCC report uses forcing (measured in watts per square metre) as inidicator of global mean change in energy balance imposed over time by changes in atmospheric composition (for example aerosols, CO2 and CH4) and other influences such as land use.

When calculated as a sum, the individual components like the ozone levels, land use, and direct greenhouse-gas emissions as well as their respective uncertainties stand for the total climate forcing from human activity, and its uncertainty which was estimated by the 4th Intergovernmental Panel on Climate Change (fig 5).

Due to the inevitable cancelling out of some of the warming effects of greenhouse gases caused by cooling effects of anthropogenic aerosols, the estimated forcing for the several components combined, that is, 1.6 W m–2 over the industrial period, is closing up to that from CO2 emissions alone (12).

Figure 5. Global average radiative forcing (RF) estimates and uncertainty ranges in 2005, relative to the preindustrial climate, for anthropogenic carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) together with the typical geographical extent (spatial scale) of the forcing and the assessed level of scientific understanding (LOSU).

The total anthropogenic radiative forcing and its associated uncertainty (5–95% confidence interval) are also shown (12). Green bar at bottom and associated uncertainty range is the estimate from the 2001 IPCC report of the total forcing projected for 2100.

Greenhouse-gas forcings are more certain than aeorosol forcings and hence the total forcing is also likely uncertain. According to Schwartz and colleagues „the century-long lifetime of atmospheric CO2 and the anticipated future decline in atmospheric aerosols mean that greenhouse gases will inevitably emerge as the dominant forcing of climate change, and in the absence of a draconian reduction in emissions, this forcing will be large“.

Greenhouse gases dominance is seen in estimates from the third IPCC report (bottom of figure 5). The projected forcing consisting of greenhouse-gas and aerosole forcings is 4 – 9 W m–2, which is comparable to forcings estimated for major climatic shifts, such as that for the end of the last ice age (Hoffert and Covey, 1992).

4. SOCIAL AND POLITICAL REPERCUSSIONS OF CLIMATE CHANGES

Although the history is filled with lessons from civilizations that crashed from their peak of welfare, we don't need to look that back into history to see how climate and environmental change can result in conflict and the breakdown of society. Rafael Reuveny, a political scientist at Indiana University, found that of 38 cases of migration directly attributable to climate change during the twentieth century, half led to conflict, some of which were violent (Reuveny, 2007). Those existing conflicts are already being worsened by the impacts of global warming.

Climate change is now being viewed as a security threat to human society, people are starting to realize that „ it's not just happening in some distant African country but that the effects could be on your own doorstep“ (Adeel et al., 2006.). A number of countries are starting to analyze danger and security risk assessment of climate change.

Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC), estimate that by 2080, 1.1 billion to 3.2

billion people will be facing water scarcity; 200 million to 600 million, hunger; and two million to seven million more homes will be hit hard by coastal flooding. Most worrying thing is that those predictions aren't even extreme scenarios.

According to a recent report by the UN, around 50 million people will be at risk of displacement caused by vast desertification over the next 10 years, causing an “environmental crisis of global proportions”. In countries such as Algeria, France, Italy, Morocco, Spain and the United States, issues of border security are gaining more attention. Migration has become an issue of increasing political importance.

For example, North African countries are having their resources stressed due to immigration from sub-Saharan Africa. Climate changes push North African nations to move north to Spain where Spanish government is trying to prevent large-scale immigration. India is facing an even greater immigration from Bangladesh due to rising sea levels. About a third of the Bangladesh is flooded during the rainy season and half of the country is situated few metres above sea level. Since 1950's, 12 to 17 million people migrated to India due to severe droughts, natural disasters and food abesence. Recent sea level risings could affect 35 million people, which is quarter of its population (Adeel, Z. et al., 2006.). India's response to prevent movement of large scale of people is rather radical. They built a 4,000-kilometre, 3-metre high barrier along the border that is guarded by army (fig 6).