Heightabove mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods. Climate change and other forces can cause sea levels and elevations to vary over time.[1]
Elevation or altitude is generally expressed as "metres above mean sea level" in the metric system, or "feet above mean sea level" in United States customary and imperial units. Common abbreviations in English are:
Accurate measurement of historical mean sea levels is complex. Land mass subsidence (as occurs naturally in some regions) can give the appearance of rising sea levels. Conversely, markings on land masses that are uplifted (due to geological processes) can suggest a relative lowering of mean sea level.[10]
I have always been interested in theological and philosophical notions that seemed to be out of reach of our current psychological and rational equipment. I, however, have always had a constant worry humming in the background whenever I thought about such things. Though rooting my thoughts in Scripture, my theologizing on the incomprehensible used to seem unruly. So, the first time I came across the categorization of propositions above, according to, and contrary to reason, I was captivated. They contained the rules for which I was looking. I soon realized that these categories were extensively in the theological and philosophical air, especially in the Enlightenment. I found that, contrary to the portrayal of this era as antagonistic to theological mysteries, it was enthralled with them. Many of its thinkers just wanted due consideration to the rules that ought to govern our discourse and thinking on these matters.[1]
The advantage of training oneself to identify the precise type of mystery, whether revelational or natural is this: it keeps us, at the very least, from mental laziness. The Trinity, for instance, is not something simply to put aside as a mystery and not to think about. There are many important implications one can glean from reflecting on the various strands of the doctrine. (Even His incomprehensibility puts us in our place when we are prideful!) Utilizing the taxonomy does force us to order our thinking as well. Are we thinking in the realm of the incomprehensible or are we producing what are truly contradictions? The former is acceptable in theologizing and philosophizing, but the latter is not.
Jonathan S. Marko is Associate Professor of Philosophical and Systematic Theology and Dean of Undergraduate Education at Cornerstone University, Grand Rapids, MI. He earned his Ph.D. in Systematic Theology from Calvin Theological Seminary. His primary area of research is 17th- and 18th-century philosophy and theology. His most recent book, on the theology of John Locke, will be published by Oxford University Press next year.
There's a variation of the same idea sometimes used in drum parts. Write one bar of the groove, then 'play x' or 'play x bars', perhaps with a squiggly line underneath (but preferably not a multirest bar, which could be confused with a multirest). The drummer may repeat literally what is written, or may be allowed some latitude, depending on where the musical style lies on the scale between Military Band and Jazz Ensemble!
For example, a one-bar repeat indicates that the material in one bar is repeated, meaning every bar in the region repeats the same material. A four-bar repeat indicates that the material in the previous four bars is repeated.
The associated images show a slash between two dots for a single-bar repeat, two slashes between two dots with the numeral 2 written above for a two-bar repeat, and four slashes between two dots with the numeral 4 written above for a four-bar repeat.
Two-bar Repeat Signs:The most common sign to designate the repeat of a two-measure phrase is a double slash with two dots on the bar line between the two measures immediately after the two measures to be repeated. The number two is typically centered over the sign, but is technically not required. A composer can use any number of two-bar repeat signs in a row. An alternate way to designate the repeat of a two-measure phrase is the use of word bis (meaning twice) centered in brackets over the phrase (shown below).
The Industrial Revolution transformed the textile industry in England. This engraving by Edward Goodall (1795-1870), originally titled "Manchester, from Kersal Moor," after a painting of W. Wylde, shows numerous industrial chimneys in the town of Manchester, England, which earned the nickname "Cottonopolis," following its transformation. Image in the public domain, from Wikimedia.
When you read or hear climate numbers, they are often being compared to average. The September 2023 NOAA global surface temperatures, for instance, were 1.44 degrees Celsius above average. That average represents a defined period of time. In this case, September was 1.44C warmer than the average September of the twentieth century.
How far the global temperature is above average depends on how you define average. For NOAA's global temperature dataset, "pre-industrial" is defined as the period from 1850-1900. For routine monthly reports, NOAA compares monthly temperatures to the 20th-century average. NOAA Climate.gov graph, based on data from NCEI.
Suffice to say, there are a lot of ways of measuring temperatures. And THEN there are different ways of combining those observations into a global dataset. (Despite these differences, all major temperature records show a similar long-term warming trend.) When NOAA releases the latest monthly climate statistics, it uses the NOAA Global Surface Temperature (NOAAGlobalTemp) dataset which blends in-ocean sea surface temperatures and 2-meter air temperatures.
The relevance of this temperature threshold was explored even more in the 2018 IPCC Special Report on Global Warming of 1.5C. In that report, and further supported by subsequent IPCC reports and other scientific literature, they found that limiting global warming to 1.5C will reduce the impacts on human systems and terrestrial, freshwater and coastal ecosystems. It made clear that every increment of global warming above 1.5C matters for the scope and magnitude of these impacts.
Remember, passing this threshold as defined in the Paris Agreement is supposed to reflect when human-caused global warming consistently exceeds 1.5C compared to pre-industrial times. That is NOT simply when average global temperatures pass that mark on any given day, month, or even year. To know when Earth has passed that threshold, we have to look at longer timescales.
Human-induced warming (blue shading) reached approximately 1C above pre-industrial levels in 2017. At the present rate, global temperatures would reach 1.5C around 2040. Stylized 1.5C pathway shown here (green shading) involves emission reductions beginning immediately, and CO2 emissions reaching zero by 2055. Graphic appears in FAQ 1.2 in the Frequently Asked Questions supplement to the IPCC Special Report on Global Warming of 1.5C.
Instead, we need to average the temperature anomalies over a period of time like 20 to 30 years. Averaging helps to smooth away any of the rough edges caused by natural warming factors and better reveals the long-term trend. That is why it can be said at the same time that global temperatures have reached 1.1C above the pre-industrial in 2011-2020 (according to the IPCC 6th assessment report), and that global temperatures in September 2023 were 1.5C above the pre-industrial.
It's also important to note that the Paris Agreement does not specify how many years should make up this long-term trend, which dataset should be used, and which time period makes up the pre-industrial period. That means different scientists, governments and groups might come to different conclusions about when Earth passes this critical threshold.
Absolutely not. Millions of people globally are already experiencing impacts of climate change in the form of extreme temperatures, heavy rains, flooding, and more. The 1.5C climate threshold is not a light switch that turns on all sorts of climate calamities. For every little bit of additional warming, the risk of negative impacts gets worse.
Temperature change is not uniform across the globe. Projected changes are shown for the average temperature of the annual hottest day (top) and the annual coldest night (bottom) with 1.5C of global warming (left) and 2C of global warming (right) compared to pre-industrial levels. Graphic appears in FAQ 3.1 in the Frequently Asked Questions supplement to the IPCC Special Report on Global Warming of 1.5C.
The 1.5C limit is sort of like a highway speed limit. Backed by plenty of science about the dangers of speeding, we know that every bit of additional speed increases the danger of an accident. There is no single speed below which the risks are zero and above which (within reason) an accident is guaranteed to occur or to be deadly. Still, we pick a limit beyond which the risks become larger than we are willing to tolerate. (Footnote 3)
Looking at what models predict for the near term (next 9 months), monthly global temperatures look to remain quite warm through the beginning of 2024 before beginning to fall from that perch as the calendar shifts into spring. This is consistent with how we know El Nio impacts global temperatures; this period coincides with the forecasted weakening of the current El Nio. (Footnote 4)
In May 2023, the World Meteorological Organization forecasted that annual global temperatures were predicted to have a 66% chance of exceeding 1.5C for at least 1 year between 2023-2027 (Footnote 2). This is consistent with how we expect continued global warming to affect temperature trends over multi-year time periods and the likelihood for a strong El Nio to supercharge warming in a given year.
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