Global Warming: trends and consequences

Recently, health officials from the U.S. Centers for Disease Control issued a travel alert for Central, South America and the Caribbean, some 14 countries and territories exposed to the mosquito-borne Zika Virus.  The alert targets pregnant women and follows reports that thousands of babies in Brazil were born last year with microcephaly, a brain disorder experts associate with Zika exposure. Babies with the condition have abnormally small heads, resulting in developmental issues and in some cases death. Some people believe that under a global rise in temperature, insects in particular are passing through their larval stages faster and becoming adults earlier. In addition, studies show that flying insects’ migratory patterns have shifted and show extensions in their boundaries.

Many of us know that the life cycle of many organisms are strongly influenced by temperature and precipitation and recent global warming analysis of long-term data sets indicate that physiology, distribution and phenology of some species of plant, animal, and insect life is affected by warming temperatures. Primarily, global warming is the problem of too much carbon dioxide in our atmosphere. As we burn fossil fuels like coal, petroleum and natural gas for energy, it accumulates and overloads our atmosphere. Also, certain waste management and agricultural practices release other gases such as methane and nitrous oxide into the atmosphere. To put it all into perspective, trapping these gases and their accumulation over time is literally changing the ecological balance of our world and those changes will effect future generations.

The effects of global climate change on the environment has already been observed. For example, glaciers are shrinking, ice on rivers and lakes is breaking up earlier, and plant and animal development has been altered. Also, heat waves resulting from global warming is presenting greater risk of heat-related illness and deaths especially to the elderly, young and people with diabetes. Scientific evidence indicates that an increase in the global average temperature above pre-industrial levels presents risks to natural ecosystems and human health.

Here are some of the facts. There is more carbon dioxide in the atmosphere today than at any other time in the last 800,000 years. With the start of industry in the 1700s, mankind began emitting more fossil fuels from coal, oil and gas into the atmosphere and the concentration of carbon dioxide has been increasing since the 19th century. Since 1870, global sea levels have risen by eight inches.  And since the 1960s, the amplitude of this oscillation has increased by 20% in Hawaii and by 40% in the Artic.

Today, ecologists, physiologists and geologists have been collecting enormous amounts of data in an attempt to predict the effects of atmospheric change on species and communities. These predictions can be explained in a broad sense and summarized into four distinct categories: effects on physiology; effects on distributions; effects on phenology, and, effects on adaptation.

Effects on physiology means that changes in atmospheric CO2, temperature and/or precipitation will affect metabolism and development in animals, photosynthesis, respiration, growth and tissue composition in plants. The effects on distribution corresponds to a shift in isotherms. As a result, species are expected to move upwards in latitude elevation towards the poles in response to shifting climate zones. Effects on phenology suggests that environmental events may lead to altering or decoupling of relationships between species thereby upsetting the ecological balance between animals. Also, effects on adaptation means species with short generation times and rapid population growth rates might undergo micro-evolutionary change “in situ” (locally or on site).

In additions to these effects, plant productivity, growth, and photosynthesis will be impacted. A recent survey showed that 63% of European butterfly species have shifted northward and extended their boundaries. Increases in mosquito-borne diseases have been reported in the highlands of Asia, Central Africa and Latin America. The mosquito that carries malaria (Plasmodium falciparum malaria) is growing in the New Guinea highlands, Tanzania and Kenya. More important, Dengue Fever, previously limited to about 1000m in elevation in the tropics at 108 C winter isotherm is appearing at lower altitudes in Mexico along with Yellow Fever becoming more prevalent in Columbia. Further, marine species are responding negatively to short-term, sea surface temperature changes. Another survey conducted on Californian reef fish assembled over a 20-year period (1974-1994) showed that colder affinity species declined from 50% to 33% and the composition changes were accompanied by substantial declines in the abundance of species, with northern species suffering the greatest reductions.

According to the U.S. Global Change Research Program, the temperature in the U.S. has increased by 2 degrees in the last 50 years and precipitation has increased by 5%. Perhaps, most important is the fact that during the decade of 2001-2010, the global average temperature has been the warmest since 1880 and nine of the warmest years on record have occurred within the last ten years.

Another consequence certainly worth mentioning is the counter-argument against global warming. It seems that there is a bevy of renowned scientists from Noble Laureate Ivan Giaever, Freeman Dyson, William Happer and others that admit that global warming is occurring but whether it is a bad thing or not has yet to be proven. Some even believe there are carbon dioxide effects that are hugely favorable. Apparently, they believe that the data is not being interpreted accurately because it does not include all the various sources of carbon emissions and that we do not understand all the details.

Further, at the International Conference of Climate Change in 2014, the question of “consensus” among the world’s scientific community was brought under scrutiny. It seems that of the proposed 97% of the world’s scientists that supported the statement that “human activity is causing most of the current global warming (or anthropogenic global warming – AGW), actually less that 1% endorsed the statement as defined. Statistics show that more than half were excluded for expressing no opinion.

And so, that debate continues. Most agree that the global temperature is increasing but a consensus on whether or not that will be responsible for devastating, catastrophic events is still not resolved. However, one thing does seem apparent, we should pay close attention to our impact on the world around us and how our activities as human beings alter the forces of nature.

Epstein, P.R. et al. (1998). Biological and physical signs of climate change: focus on mosquito-borne diseases. Bull. Am. Meteorol. Soc.79, 409–417; Keeling, C.D. et al. (1995). Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980. Nature 375, 666–670; Keeling, C.D. et al. (1996). Increased activity of northern vegetation inferred from atmospheric CO2 measurements. Nature 382, 146–149; Reid, P.C. et al. (1998). Phytoplankton change in the North Atlantic. Nature 391, 546; Parmesan, C. et al. (1999). Polewards shifts in geographic ranges of butterfly species associated with regional warming. Nature 399, 579–583; Holbrook, S.J. et al. (1997). Changes in an assemblage of temperate reef fishes associated with a climate shift. Ecol. Appl. 7, 1299–1310; Pounds, J.A. et al. (1999). Biological responses to climate change on a tropical mountain. Nature 398, 611–615; Johnson, N.K. (1994). Pioneering and natural expansion of breeding distributions in western North American birds. In A Century of Avifaunal Change in Western North America (Jehl, J.R. and Johnson, N.K., eds), pp. 27–44, Cooper Ornithological Society. Hughes, L. (2000). Biological consequences of global warming: is the signal already. Tree 15:2, 56-61.