Читать книгу Introduction to Energy, Renewable Energy and Electrical Engineering - Ewald F. Fuchs - Страница 13

Figure P.1 illustrates the present warming distribution throughout the earth as published by National Aeronautics and Space Administration’s (NASA) Goddard Space Flight Center [1] where the measured global temperature during 2014 – indexed to the average values during the twentieth century – has increased by 0.68 °C. This average temperature increase, driven chiefly by human influence on the global carbon cycle as illustrated in Figure P.2 through deforestation and unrelenting emissions of greenhouse gases, captures our rationale for writing this book.

Figure P.1 Measured temperature anomalies during 2014 referring to the average values during the twentieth century, where the global average temperature in 2014 has increased [1] by 0.68 °C.

Figure P.2 CO₂ variation and increase [2] during the past 800 000 years.

A 2008 paper by NASA scientist James Hansen [3] shows that the true gravity of the situation due to human, or anthropogenic, effects on the environment includes impacts on biophysical environments, biodiversity, and other natural resources. Hansen set out to determine what level of atmospheric carbon dioxide (CO₂) society should aim for “if humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted.” His climate models show that exceeding 350 parts per million (ppm) CO₂ in the atmosphere would likely have catastrophic effects. We have already surpassed that limit because environmental monitoring showed concentrations of around 400 ppm in 2014. This is particularly problematic because CO₂ and other greenhouse [4] gases (see Table P.1) remain in the atmosphere for a long time. Even if we shut down every fossil‐fueled power plant today, existing greenhouse gases will continue to warm the planet.

Table P.1 Greenhouse gases and their chemical formula, anthropogenic sources, atmospheric lifetime, and global warming potential (GWP) [4].

Greenhouse gas	Chemical formula	Anthropogenic sources	Atmospheric lifetime [1](years)	GWP [2] (100‐year time horizon)
Carbon dioxide	CO2	Fossil fuel combustion, land‐use conversion, cement production	~100 [1]	1
Methane	CH4	Fossil fuels, rice paddies, waste dumps	12 [1]	25
Nitrous oxide	N2O	Fertilizer, industrial processes, combustion	114 [1]	298
Tropospheric ozone	O3	Fossil fuel combustion, industrial emissions, chemical solvents	Hours‐days	NA
CFC‐12	CCL2F2	Liquid coolants, foams	100	10 900
HCFC‐22	CCl2F2	Refrigerants	12	1 810
Sulfur hexafluoride	SF6	Dielectric fluid	3 200	22 800

The climate conundrum [5] is best illustrated in Figure P.3, which shows two sharply divergent pathways for CO₂ emissions: “business as usual” and the “best‐case scenario” of CO₂ emissions in billions of metric tons. Figure P.4 depicts the CO₂ accumulations in the atmosphere for “business as usual,” “best‐case scenario,” “Hansen model,” and “safety threshold” scenarios. Achieving the deep cuts in carbon emissions required to step down from the business‐as‐usual trajectory to one with increased probability of climate stability is a monumental task. Fossil fuels and extractive industries are currently deeply interconnected with Western lifestyles, infrastructure, and typical economic development pathways. Making the leap will require political commitment to pricing carbon, continued innovation in low‐carbon energy and storage, and the imagination and flexibility to envision – and bring about – a more resilient future.

Figure P.3 Possible emissions pathways [5], billions of metric tons of CO₂.

Figure P.4 Divergent scenarios [5] for atmospheric CO₂ in parts per million (ppm).