A History on Global Temperatures, Life on Earth, and Global Warming

  

A few days ago, I circulated this piece of news that Iran is in the grip of a very severe heat wave here:

Unprecedented heat’: Iran begins two-day nationwide shutdown amid soaring temperatures.

https://www.cnbc.com/2023/08/02/iran-begins-two-day-nationwide-shutdown-due-to-soaring-temperatures.html#:~:text=Many%20Iranian%20cities%20and%20towns,39%20degrees%20Celsius%20on%20Wednesday. 

Heatwave prompts fears of hospitals in Iran.

https://www.sinardaily.my/article/203406/world/news/heatwave-prompts-fears-of-hospitals-overcrowding-in-iran

I then commented very briefly this is a localized effect and may or may not reflect in the overall changes in the rise in global warming.

I then received this question from Ir. CK Cheong, a good engineering friend of mine. He asked:

“Good morning, dear Dr Lim, is the rate of cooling against the rate of heating really so much different that planet earth will warm up so rapidly”.

I suppose he knew I knew something about astronomy and also about the evolution of life and its mystery, he may have thought I could answer.

I shall try. I shall make the answer / explanation as simple as possible. 

This answer is also delicated to sister Sonia Soon who requested me to write an article on climate change about 10 days ago.

I hope this helps for both of you.

 

Jb lim 

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My views here:

During the accretion of Earth 4.543 billion years ago, Earth was searingly hot at between 3,925 and 4,125 Kelvin (4,000 Kelvin). Then about 4.5 billion years ago or 43 million years later, the temperature dropped drastically from about 4,000 Kelvin to 350 Kelvin (80 degrees Celsius), a difference of 3,650 Kelvin. 

After it cooled down considerably, it was then called the "Haden Earth". This fast cooling was because of the huge difference in the temperature gradient when it was first formed, after it was  suspended in deep space for 43 million years in almost absolute zero temperature since the rate of heat loss of a body is directly proportional to the difference in the temperatures between the body and its environment to obey Newton's law of cooling.

In another words, a very hot body cools down faster than the same body at a lower temperature. Once the very hot temperature drop down sufficiently, it will take a longer time to cool down to a staple temperature like currently. 

Thus the Earth since its accretion began to cool down dramatically to current average temperatures of 59 degrees F (15 degree C). Scientists made these approximations by looking at the oxygen and silicon isotopes in marine rocks.

 

Another site gave these estimates:

 

How Hot Were the Oceans When Life First Evolved? | News | Astrobiology (nasa.gov)

 There is geological evidence to suggest that 3.5 billion years ago, during the Archean Eon, the oceans were 55 degrees to 85-degree C. The Archean Eon was a violent period 4.6 to 4.0 billion years ago in Earth’s geological history. Following that in the Archean Eon, Earth finally started to cool down with a more stable climate.

 

We know that as ocean temperature drops, there are higher amounts of oxygen -18 and silicon-30 isotopes found in shale rocks on ocean and sea floors. In other words, by looking at the ratio between the heavier and lighter oxygen isotopes and silicon isotopes scientists were able to tell the temperature in the early stages of this planet.

The average warming of this Earth is not even. If we look at it as a whole the sea is cooler than the land mainly because a larger proportion of the Sun’s heat energy is used to evaporate water rather than being absorbed to increase the sea surface temperature. Where there is a lot of evaporation such as the sea, less heat is absorbed compared to dry land where more heat is absorbed quickly but also releases quickly from lack of water for evaporation. There is also more heat flowing to the land than heat flowing to the seas by day. It takes time for water to be heated up.  

 

At night the sea is warmer than land due to the heat capacity of water being higher than on solid land. This results in the air above the sea becoming warmer and the air above land is cooler. 

 

During daylight hours, when sunlight pours its heat energy on the surface of the waters, it absorbs much of the radiation and stores them although much is also lost by evaporation.The stored energy then radiates back out into the atmosphere at night when temperatures drop considerably. This helps keep temperatures over the oceans comparatively warmer compared to the land that stores lesser energy although it heats up faster and radiates them faster.

 

When night falls, the land cools down quickly than that of water causing high pressure over land and hot air above the water causes low pressure over it. The wind then blows from higher pressure to lower pressure, so during night, cool breeze blows from land to sea.

 

 The evaporation from the oceans and seas means that the sea warms less slowly than the land but it also causes more heat to flow from the oceans to the land than from land to oceans, making the difference in temperature between the oceans and land to surge even more.

 

 Scientists estimate that about 80 – 90 % of the warming of the land is caused by heat transfer from the oceans. The dynamics of heat transfer from land to sea, and from sea to land is quite complicated depending on how much mass water and land ratios on different parts of the world.  

 

Generally on the whole, the Earth emits out more heat into space than it receives from the Sun. This may explain why the Earth cooled down initially very fast after her accretion 4.543 billion years ago when it was created. It was then bizarrely hot at between 3925 and 4125 Kelvin. Then it cooled down slowly after that as already mentioned. 

 

Many land areas are now experiencing greater warming than the global average. For instance, when global warming above pre-industrial levels has an average value of 1.5°C across the Earth, the average change across some regions of land mass could be twice this value. 

Industrialization and human activities generates greenhouse gases like carbon dioxide and methane from farm animals and decaying matter.

Chlorofluorocarbons (CFCs) that was once used as a refrigerating gas, now banned because of their effects on the ozone layer is also a powerful greenhouse gas. 

These gases trapped heat from the Sun from being radiated out into space at night, causing global temperatures to rise. 

But let’s have a look at what the global temperature was like in ancient times when Earth was first created. Here is the brief scenario:

 

Astronomical Big Bang of the Universe began 13.8 billion years ago. The accretion of Earth took place 4.543 billion years ago. 

At the time of the accretion of this Earth, scientists using geochemically coherent models estimated the Earth was incredibly hot to the tune of between 3925 and 4125 Kelvin. The atmosphere and the climate millions of years later may be still over 2,000 Kelvin.  

 

When Earth continued to cool down probably to less than 80 degrees Celsius (353.15 Kelvin) life became possible. We can affirm Earth and the history of evolution of life on Earth began 4,200 million years ago when the atmosphere and oceans were formed. Then 4,000 million years ago, prebiotic chemistry became possible.

 

This was followed by the evolution of life 3,800 million years ago when the RNA world came into existence shown by the first chemical fossil available (viruses). Then 3,600 million years ago the first DNA protein life came into existence which was followed 3,500 million years ago when LUCA: Archaea / Bacteria split and also photosynthesis (autotrophy) began.  Following that event 2,700 – 1,900 million years ago the first eukaryotes / sexual reproduction became possible.

It may have been possible before 3.9 billion years ago for life to live and adapt to extreme conditions such as extreme temperature, radiation, salinity, and pH level. These are called extremophiles, which we now understand can live at temperatures up to 120°C (Kashefi & Lovley 2003) and in depths of more than 3 km (Lin et al. 2006) by colonizing deep habitats (Abramov & Mojzsis 2009).

Average global temperatures during much of the Neoproterozoic Era (1 billion to 541 million years ago) were cooler of around 12 °C than the average global temperatures of around 14 °C of the present day, whereas the global temperature of Cambrian radiation when there was an explosion of all kinds of life on earth averaged 22 °C.  

When life began to flourish on Earth there were considerable temperature variations in the atmosphere and the oceans from records of global temperatures. Variations and estimates have been forwarded through the stages of earth’s history since the end of Pleistocene glaciation, principally during the current Holocene epoch. Some of the records from geological evidence date back millions of years ago. 

 

The Pleistocene has been dated from 2.580 million (±0.005) to 11,650 years BP with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP. It covers most of the latest period of repeated glaciation, up to and including the Younger Dryas cold spell.

 

The Younger Dryas was the last stage of the Pleistocene epoch that bridged from 2,580,000 to 11,700 years ago (BP- before present time), and it preceded the current, warmer Holocene epoch.

 

During the Pleistocene Epoch there was a great diversity of mammals that evolved including mammoths, mastodons, giant sloths, several llama-like camels, and tapirs. And it was the last epoch of native horses that lived in North America. The horses were both abundant and diverse.

 

The Holocene Epoch is the current period of geological time, during the age of man. We sometimes call it the Anthropocene Epoch, because its crucial characteristic is the global changes caused by human activity. This term can be deceptive because modern humans were already well established long before the epoch began. 

 

The Holocene Epoch began 12,000 to 11,500 years ago at the close of the Palaeolithic Ice Age around 40,000 to 10,000 years ago when humans started making tools and weapons which unfortunately still continues till today together with his other destructive needs such as deforestation, industrialization, greenhouse gases emission which we believe are the main cause of climate change.

 

We have evidence of climatic changes between 800,000 years ago till the present time from gasses trapped in ice cores dug up.  Other studies on ancient climate cover the period 12,000 years ago till the present time. Some studies looked at the global temperature between 1,000 – 2,000 years ago till the present time by taking tree rings measurements from ice cores.

 

However, some of these temperature changes were not created by human activities, but by small changes in the energy it receives as Earth orbits around the Sun.

 

This slow temperature change, averages around 0.5°C over the past 10 thousand years giving an environment that is still mild enough to support life and human activities.

 

In the past the earth was much colder. There was the ice age.  Approximately 40 million years ago there were cycles of glacial and interglacial are part of ice age that began with the glaciation of Antarctica and growth of continental ice sheets in the Northern Hemisphere. Gradual changes in Earth's climate were a frequent occurrence during the Earth's 4,540-million-year existence.

 

Greenland probably has the most abrupt climate changes, and there are no other records that can show the same elsewhere.

 

Methane concentration in trapped gas in the ice core bubble was found to be significantly higher in Greenland samples than in the Antarctic of similar age. This means methane as a greenhouse gas may have warmed up Greenland more than in the Antarctic. This effect may apply elsewhere as greenhouse hot spots.

 

Ice core records from Antarctica

The Antarctic ice sheet began in the late Eocene shown by drilling records of 800,000 years old in one of the elevations (Dome Concordia) in the Antarctic. This is the longest available ice core records in Antarctica, although there are a lot of isolated studies elsewhere.

 

The exclusivity of the Antarctic ice sheet and ice core not only accounts for the global temperature changes, but also encloses a lot of information about the global biogeochemical cycles, climate dynamics and abrupt changes in global climate.

By comparing current climate records with ice core records in Antarctica showed that there is polar amplification. This is a phenomenon that any change in the net radiation balance such as greenhouse intensification tends to produce a larger change in temperature near the poles than in the planetary average. 

 

This is commonly referred to as the ratio of polar warming to tropical warming. polar amplification. Although Antarctica is covered by the ice core records, the density is rather low considering the area of Antarctica. Drilling stations in the Antarctic give scientists an idea of climatic changes.

 

The ice core records from low-latitude regions, although not as common as records from polar regions, nevertheless still provide much information for us to compare regional changes in global temperatures and greenhouse effect. Ice cores in low-latitude regions are usually located in high altitude areas. The Gudiya record is the longest record from low-latitude, high altitude regions, which bridges over 700,000 years. 

 

Scientists found evidence from these records that the Last Glacial Maximum (LGM) was colder in the tropics and subtropics than previously believed.  Records from low-latitude regions showed that the 20th century was the warmest period in the last 1000 years.

 

Paleoclimatology is the study of ancient climate in Earth’s history. Most of the studies on climate change were during the Holocene epoch 10,000 years ago.

 

The Younger Dryas date from around 12,900 to 11,700 years ago.  During this period there was  a return of glacial condition  which temporarily overturned climatic warming after the Last Glacial Maximum (LGM), that  lasted from approximately 27,000 to 20,000 years ago.

 

The Younger Dryas was the last stage of the Pleistocene epoch that spanned from 2,580,000 to 11,700 years ago or BP to mean “before the present time” and it heralded the current, warmer Holocene epoch. The Younger Dryas was the most severe and longest lasting of several interruptions to the warming of the Earth's climate It was preceded by the Late Glacial Interstadial, a period of warmer climate that lasted from 14,670 to 12,900 before the present time.

 

The Younger Dryas was a millennium of long cooling. The Holocene Climatic Optimum was mostly warmer than in the 20th century, although there were regional variations since the beginning of the Younger Dryas.

 

There are many methods of measuring climatic change. Tree rings and ice cores look at climate from 1,000–2,000 years before present).

 

Proxy measurements are also used to reconstruct the temperature record before the historical period. Quantities such as tree ring widths, coral growth, isotope variations in ice cores, ocean and lake sediments, cave deposits, fossils, ice cores, borehole temperatures, and glacier length records are interconnected with climatic fluctuations. From these, proxy temperature reconstructions of the last 2000 years have been presented.

 

Scientists use several methods to determine climate and climate change in the ancient past. Among them are looking at tree rings, ice cores, boreholes, and corals.  They may also look at records of good and bad harvests; dates of spring blossom or lambing; extraordinary falls of rain and snow; and unusual floods or droughts. 

 

All these records albeit indirect give clue what the climate and temperature were then.

 

What they found was global mean surface temperatures over the last 25 years have been higher than any comparable period since AD 1600, and probably since AD 900.

 

There was a Little Ice Age on AD 1700. There was also a Medieval Warm Period around AD 1000, but this was not a global phenomenon.

 

Recent suggestion implies that there was a sudden and short-lived climatic shift between 2200 and 2100 BCE occurred in the region between Tibet and Iceland, with some indication suggesting a global change. The result was a cooling and reduction in precipitation. Civilizations in the past may have disappeared due to climate change.

 

Currently, satellites, weather balloons, radiosonde, microwave sounding units on satellites, as well as Remote Sensing Systems have been used to look at temperatures in the troposphere.

 

It was found there was a global average increase in temperature between 1978 and 2019 by 0.130 degrees Celsius per decade. Remote Sensing System found a trend of 0.148 degrees Celsius increase in temperature per decade up to January 2011.

 

In 2004 scientists found trends of +0.19 degrees Celsius per decade when applied to the Remote Sensing System dataset. Others found 0.20 degrees Celsius per decade up between 1978 and 2005, since which the dataset has not been updated.

 

Thermometers were used from 1850 till the present.

 

Temperature recording instruments like the thermometer measure the temperatures within Earth's climate based directly on the air temperature and ocean temperatures. 

 

This is unlike indirectly from tree rings and ocean sediments as there is no way of using instruments and thermometers to measure directly what happened thousands of years ago. Instruments collect data directly from thousands of meteorological stations, buoys and ships around the globe. 

 

Most of the measurements are done in populated areas compared to sparsely populated areas such as polar regions and deserts, as well as over many parts of Africa and South America.

 

Electronic measuring sensors are more commonly used nowadays which transmit data automatically instead of using a manually read thermometer.

 

They will compare global average temperature datasets from various scientific organizations to monitor the progress and extent of global warming.

 

The longest record of temperature is the Central England temperature data series, which began in 1659 while longest quasi-global records start in 1850. It is not just ground-based temperatures, but currently scientists make use of weather balloons fitted with radiosondes, as well as using satellites and aircrafts to measure temperatures high up in the atmosphere to look at temperature changes up there.

 

Over the last decades, global surface temperature datasets have been augmented by measuring ocean temperatures at various depths for their ocean heat content.

 

These combined records show there is a rise in global average surface temperatures which we call global warming largely due to emission of carbon dioxide, methane and other greenhouse gasses due to human activities.  On the average, based on multiple independent datasets that combines   land and ocean surface temperatures, the warming trend is 1.09 °C, ranging between 0.95 to 1.20 °C from 1850–1900 to 2011–2020, The tendency is quicker since 1970s than in any other 50-year period over at least the last 2000 years.  Within this upward trend, there is short-term unevenness due to natural internal changeability such as ENSO, volcanic eruption even though the warming trends have been consistently high.

 

See also other explanation on this dilemma of ours here:

 

https://scientificlogic.blogspot.com/search?q=global+warming

 

https://scientificlogic.blogspot.com/search?q=over+population

(A 3,139 worded answer in 16  pages for Ir CK Cheong and Sister Sonia Soon)