Learning Check Point

Anthropogenic Factors

Please take a few moments to think about what you just learned, then answer the following questions to test your knowledge.

Question 1 - True or False

As we summarize the earlier content, we have explored a vast number of phenomena that all have some impact on observed sea-level changes. Some of these are driven by natural processes intrinsic to the functioning of Earth systems, some are driven by extrinsic factors governed by processes operating in our solar system. One major variable that has only recently in Earth's history played a role in sea-level change is the anthropogenic variable. Although debates continue to rage about the degree to which humans are contributing to sea-level change, relative to other factors, it is clear that the use of fossil fuels and destruction of productive habitats (rain forests, marshlands, etc.) worldwide have increased the output of greenhouse gases as well as reduced the rates at which carbon dioxide is consumed by photosynthesizers. As these processes continue, the potential exists for runaway warming, especially if the oceans continue to warm, rise, and succumb to bottom-water anoxia in the absence of glaciers and thermohaline circulation.

Is the following statement true or false?

a. True
b. False

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Question 2 - Multiple Choice

Analysis of actual measurements of sea-level position (combined with various proxy datasets) for the last 100 years or more show a clear average global trend of transgressive mean sea-level. However, recent observations and measurements, which if accurate are potentially alarming. NOAA scientists and others have been measuring heat content of the oceans, including in the upper layers of the ocean. These data reveal that a pronounced warming of the oceans is occurring, and not only that, but the warming may not be linear.

How does this data compare to the measurements of sea-level from satellites and from tide-gauge stations?

a. Over the last five decades, ocean warming data reveal accelerating warming since the 1960's, average tide gauge measurements also show acceleration as rates of SLR appear to be increasing from 2 mm/year to potentially as much as 7 or 8 mm/year in some areas as of the last decade of measurements.
b. Ocean warming data reveal accelerating ocean warming since the 1960's, but this is contrary to the trends of tide gauge measurements that show evidence for stabilization of sea level rise rates at about 2 mm/year since the 1800's.
c. Ocean warming data at the surface reveal linear warming trends since the 1960's, but recent glacial melting has helped lower ocean temperatures at high latitudes and this is helping to cool the deep ocean layers. This counteracts the warming in surface layers.
d. Five-year running averages (pentadal data) of ocean heat change clearly shows a non-linear warming with an overall decrease in the rate of warming in the 2000's. So although sea-levels as measured by instrumental data are still rising, the rate of rise is decelerating relative to heat content of the ocean.

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Question 3 - Multiple Choice

Why do scientists spend so much time looking at the geologic record of sea-level and climate change?

a. It is important to study how and why dinosaurs or trilobites went extinct so that we can see if can prevent current species from going extinct.
b. It is important to determine how the earth system works to prevent climate change from ever happening again.
c. It is important for scientists to do research so they can get grant funding to support the educational mission of modern society.
d. It is important for scientists to detect patterns that can be used to make predictions about the future to best protect lives and property.

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