Page 17 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

Introduction Chapter | 1 9

FIG. 1.8 Monthly mean atmospheric carbon dioxide concentrations at Mauna Loa Observatory,
Hawaii, 1958–2016—the longest record of atmospheric CO 2 measurements in the world. (Data
from NOAA Earth System Research Laboratory.)

As mentioned, the Earth’s climate has always varied. Climate change
sceptics often use this fact to argue that the recent change in the Earth’s
climate may be due to natural processes (that we may or may not know), and
it is not necessarily due to the combustion of fossil fuels. It is true that the
Earth has experienced warmer periods, and higher sea levels in the past, when
humans did not exist. Scientists have rejected this argument by studying the
concentration of carbon dioxide in the atmosphere over many thousands of
years. This has been achieved by the analysis of air bubbles trapped in Antarctic
ice cores that extend back to 800,000 years. The Carbon Dioxide Information
Analysis Center (CDIAC), which serves as the primary climate-change data and
information analysis centre of the United States, keeps the record of carbon
dioxide data collected at several locations in Antarctica. Based on these data,
we can plot the time series of atmospheric carbon dioxide concentration over
thousands of years (Fig. 1.10). As we can see, before the industrial revolution,
the concentration was always below 300 ppm. The current level of CO 2 in the
atmosphere (406 ppm), which is well above 300 ppm, is directly the result of
burning fossil fuels. Because we are sure that carbon dioxide is a GHG, we can
conclude with certainty that human activities have resulted in global warming.
It has now been accepted that it is too late to stop global warming, and much
policyisnowfocussedontryingto limit future global warming. The 2016 Paris
Agreement, signed by 194 countries, aims to keep the increase in global average
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temperature to well below 2 C above preindustrial levels, and to pursue efforts
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to limit the temperature increase to 1.5 C above preindustrial levels, recognizing