ENVS 202 On-line Access

Important:

If you believe that global warming is a real problem then take a GREEN strip from the Sacred Box of Sampling.

If you believe that global warming is a hoax or a myth or not all that alarming or important take a RED strip

Looking More at Data

First a return to the Salmon issue:

White Men Luv Fish

• There are international implications
• Important role of El Nino
• Real time data collection
• Significant increase in Canadian Harvests
• Fishing Technology in Alaska
• Notes from a 50 year Alaska Native

The above documents and data strongly suggest that a significant reason for Columbia river salmon decline is due to increased harvests in Alaska and Canada.

This is likely a reflection of where the Salmon are and this is strongly coupled to decadel climate changes in the Alaska-BC-PNW region.

This implies, that at any particular point in this region, over timescales of 50 years, salmon counts/catches will be cyclical in nature.

So, be careful what you are told without being allowed to see the larger picture:

	Graph shows total salmon catch off the coast of North America (including Alaska).
Decline of In-River catches which is frequently used as the "best" indicator for overall salmon decline in the Columbia River System:	Implication is that increases in ocean catch are directly responsible for decreases of in-river catches also shown.

Looking at more data to find significance or not:

Another Case: US Tornado Frequency:

This is the distribution of verified tornadoes in the American Midwest from the period of 1953--1993:

Is the apparent recent increase significant?

• Excluding the last 4 years, the mean number of tornadoes is 747 with a dispersion of 162 and a mean error of 27
• For the last 4 years, the mean number of tornadoes is 1172 with a disperion of 76 and a mean error of 38 (the mean error is larger because N is smaller)

  Again the means are similar so we get

• M1-M2 = 1172 -747 = 425
• 1.5E1 = 1.5*27 which is around 45

• 425/45 = 9 --> EXTREMELY SIGNIFICANT indicating a real effect has increased the tornado frequency --> observation or physical?

Another Case: Urbanization and the Weather

Does Urbanization produce a microclimate in the sense that urban areas are getting warmer.

Where the data is

Here are some results for Washington DC average Tempearture:

• 1960-1990: 14.78 +/- 8.5 N=360
• 1960-1970: 14.26 +/- 8.8 N=120
• 1970-1980: 15.25 +/- 8.3 N=120
• 1980-1990: 15.01 +/- 8.5 N=120

Note that the dispersions are all very similar in these periods. The square root of 120 (number of data samples) = 11.

Error in the mean for 1960-1970 = 8.8/11 = 0.80

Error in the mean for 1970-1980 = 8.3/11 = 0.75

(M1-M2)/1.5E1 = 15.25-14.26/(1.5*.8) = 1/1.2 = 0.83 --> no significant increase. A significant increase would be hard to detect in this data because the instrinsic dispersion is large.

Let's look at the case for Berkeley CA:

• 1960-1970: 13.67 +/- 3.1 N=120
• 1980-1990: 14.32 +/- 3.0 N=120

The error in the mean is a lot less because the disperion is less. The mean error is approximately 3/11 = .27

So for Berkeley we have: 14.32-13.67/1.5(.27) = .65/.40 = 1.65 --> still not significant but a lot more significant than the case for Washington DC.

This indicates that Berkeley is a better site for this study than Washington DC since the natural climate variations in DC are more severe and hence the signature of a small effect will be much more difficult to get out of the data.

Now, what do you make of this data?

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