The Earth is about 4.5 billion years old, and it’s climate has varied greatly and gone through different periods throughout that time.
In the guide below, we’ve outlined:
– A timeline of Earth’s climate, and how it’s changed over the last century, through to the last millions of years
– How warm the Earth’s climate might have got throughout history
– What ‘abrupt climate change’ is, and how much as well as how fast Earth’s climate might have changed throughout history during these events
– Other points related to Earth’s climate history
Summary – Earth’s Climate Throughout History
Earth’s Climate Throughout History (& A Timeline)
Below, we’ve outlined what Earth’s climate and temperature might have been like throughout the following time periods:
– 1850 to now
– The last 20,000 years (back to roughly 20,000 BC)
– The last 650,000, to 1 million years
– Millions of years ago, and beyond
How Warm Earth Got Throughout History
There might have been several periods of time throughout Earth’s history where the Earth got much warmer than it is now
We list those time periods and temperatures below
Abrupt Climate Change
Abrupt climate change differs to regular climate change, as it occurs on much shorter time scales e.g. over decades, as opposed to centuries or millenia
Below, we outline some abrupt climate change events that may have happened throughout Earth’s history i.e. how fast and how much the temperature changed during those events
We also explain that it might be difficult to predict abrupt climate change events that might happen in the future, and how abrupt climate change may still be somewhat of an unknown in several aspects
What Devices/Technology & Data Are Used To Determine Or Approximate Earth’s Climate
There’s a range of devices and technology, as well as data that are used to determine or approximate Earth’s climate (now, and throughout history)
We list the more recent devices/technology that have been used since 1850, and also the data that’s used for older or more ancient climate approximations
Potential Uncertainty With Determining Earth’s Climate From The Past
There may be uncertainty with determining Earth’s climate prior to 1850 – especially the further back in Earth’s history we go (i.e. millions and billions of years ago)
We provide more information on why these climate records might be approximations, guesses, or qualitative in nature only (as opposed to quantitative) in the guide below
A Level Of Speculation In Determining Or Projecting Earth’s Climate
Overall, there might be unknowns across some aspects of determining or projecting Earth’s climate.
For example, there might be a lot more certainty in the direct measurements of Earth’s climate and temperature today compared to most of Earth’s history where these measurements weren’t available.
Additionally, there might be variables and uncertainty about projecting the general climate or specific climate events like abrupt climate change events in the future.
These things might be taken into account when looking at or assessing Earth’s climate.
Global vs Regional Climates & Temperatures
It’s also worth noting that the temperatures and climates listed in this guide are global, and not regional.
Regional climates and temperatures can obviously differ from the average global climate or temperature
Earth’s Most Recent Climate History Since 1850
The data below might illustrate that, since 1850:
– The global average near-surface air temperature has increased by 0.8 to 0.9 degrees celsius since 1850
– Majority of the warming since 1850 has occurred since 1975, and some of the warmest years on record since 1850 have occurred in the last few decades
– The rate of recent warming is claimed to have happened faster than most climate shifts that have happened in the past
– Very recently in the last decade or two, warming may have slowed somewhat across some multi year periods
… globally averaged near-surface air temperature (global average temperature) rose by around 0.8°C between 1850 and 2012 (science.org.au)
What The Significance Of The Recent Warming Trend Since 1850?
While there have been past periods in Earth’s history when temperatures were warmer than they are now, the rate of change that is currently taking place is faster than most of the climate shifts that have occurred in the past … (climatecentral.org)
From science.org.au: ‘Most past changes in global temperature occurred slowly, over tens of thousands or millions of years …’
The change in global surface temperature [up to 2019], relative to 1951-1980 average temperatures, is 0.9 degrees celsius (climate.nasa.gov)
sciencealert.com has an infographic that shows the global temperature spiking in the 20th century around 1950/1960
This is when industrial revolution hits, and coincides with a large increase of fossil fuel based emissions from human activities
Two-thirds of the [recent] warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade (earthobservatory.nasa.gov)
The 10 warmest years on record [since 1880] have all occurred since 1998, and 9 of the 10 have occurred since 2005 (climate.gov)
The rate of average surface warming has slowed since 2001 … (science.org.au)
science.org.au also lists the reasons for this slowing:
‘… decadal variability in the ocean-atmosphere system which has redistributed heat in the ocean, and several temporary global cooling influences have come into play including unusually weak solar activity, increased aerosol production, and volcanic activity’
Earth’s Climate Since 20,000 BC (Roughly The Last 22,000 Years)
The data below might illustrate that, in the last 22,000 years:
– Earth had it’s last ice age about 22,000 years ago, and the climate was colder than it is now
– Roughly 20,000 years ago, gradual warming began after the ice age
– For most of recorded human civilisation, in general over the past 12,000 years, Earth’s climate has been unusually stable, with gradual and predictable warming, mixed in with some cooling
sciencealert.com has an infographic going back the last 22,000 years, to 20,000 BCE.
Some of our paraphrased notes on that infographic are:
[In 20,000 BCE, Earth was 4.3 degrees Celsius colder than it was in the late 20th century, and was in the peak of the last ice age]
[Changes in Earth’s orbit at around 18500 BCE meant that polar ice was exposed to more sunlight, and the warming period began]
[In the past 12,000 years, the climate has been relatively stable, and has experienced some gradual and relatively predictable heating, mixed in with some temporary periods of cooling]
Between 9000 and 8500 BCE … temperatures hit modern levels, and continued to rise
[In the 21st century, and after the Industrial Revolution, temperatures began to rise at a much quicker rate as CO2 levels have also increased]
View the full infographic at sciencealert.com
Over the last few thousand years … which includes most recorded human history … [Earth’s] climate [has been] unusually stable.
Earth’s Climate The Last 650,000 To 1 Million Years
The data below might illustrate that, in the last 650,000 to 1 million years:
– Earth has gone through seven to ten relatively predictable ice age cycles, where the global temperature has also risen and fallen in a relatively predictable way along with these cycles
– The last ice age came to an abrupt end, where Earth then transitioned to the modern climate we see today
Last 650,000 Years
Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization.
Last 800,000 To 1 Million Years
science.org.au has a graph showing the last 800,000 years of globally averaged surface temperature:
‘Over the past million years, Earth’s globally averaged surface temperature has risen and fallen by about 5˚C in ice-age cycles, roughly every 100,000 years or so … ‘
Also from science.org.au:
[Earth’s climate has] gone through ten major ice age cycles over approximately the past million years …
Earth’s Climate Millions Of Years Ago, & Beyond
The data below might illustrate that, in the 1 million plus years:
– About 3 million years ago, temperatures might have been warmer than they are now, and the last 3 millions years in general might have consisted of cycles of both colder and warmer periods
– About 10 to 15 million years ago, temperatures might have been warmer than they are now
– Beyond 10 to 15 million years ago, temperature fluctuations might have been substantial and extreme in some instances
– Overall, projections about the Earth’s climate a million plus years ago, and especially hundreds of millions of years ago or more, might contain a lot of speculation, as well as be more qualitative in nature
Under 10 Million Years Ago
The last 3 million years have been characterized by cycles of glacials (colder periods) and interglacials (warmer periods) that are part of a deepening phase within a prolonged ice age. (wikipedia.org)
Several million years ago … global average temperature was a few degrees higher than today and warm, tropical waters reached much farther from the equator, resulting in very different patterns of ocean and atmospheric circulation from today (science.org.au)
… around 3 million years ago … Arctic temperatures were 11 to 16°C warmer … Global temperatures over this period is estimated to be 3 to 4°C warmer than pre-industrial temperatures (skepticalscience.com)
10 To 15 Million Years Ago
[it is estimated that] 10 to 15 million years ago temperatures were substantially warmer than they are now [and, humans didn’t exist at this point in time] (climatecentral.org)
Up To Hundreds Or Thousands Of Millions Of Years Ago
Prior to 5 million or 100 million years ago [… guesses about climate patterns are] more … qualitative [or] more approximate (and not as accurate) …
The following three reports available at wikipedia.org have various images which attempt to reconstruct or estimate Earth’s temperatures and climate at various periods going up to hundreds of millions of years back:
‘Earth’s Global Temperature Record’
‘Earth’s Geologic Temperature Record’
‘Earth’s Global Average Surface Temperature’
wikipedia.org includes descriptions about Earth’s climate at the following time periods (paraphrased and summarised):
40 Million Years Ago (there may have been a more extended ice age began around this time)
65 Million Years Ago (there may have been abrupt thermal spikes around this time caused by the release methane)
66 to 100 Million Years Ago (average global temperatures may have reached some of their highest in the last 200 million years)
542 Million Years Ago (may have been fluctuating temperatures during this time)
1000 Million Years Ago (there may have been two or more major glaciations at this time)
Prior To 1000 million years ago, wikipedia.org specifically mentions:
‘… evidence of temperature changes and glaciation is usually too scattered and sporadic to draw firm conclusions though it seems likely that temperature fluctuations were also substantial during this period [and temperatures could have been much higher than today]’
The Last Billions Of Years
Earth’s climate has changed dramatically many times since the planet was formed 4.5 billion years ago (science.org.au)
How Warm Did Earth’s Climate Get Throughout History?
As we mentioned above, determining Earth’s climate millions of years ago might involve speculation.
So, the following data may be more speculative than definitive.
However, wikipedia.org has some information of what might have been some of the warmest periods in Earth’s history.
Those times might have been around:
– 65 millions years ago
– 66 to 100 million years ago
– 100 million to 542 million years ago
– Additionally, some abrupt climate change events in the past, which we list further below in this guide, may have pushed temperatures up relatively high
Some of the data below suggests temperatures could have been up to 8 degrees celsius higher than today’s temperature
The following information is from wikipedia.org …
About 65 million years ago
During the PETM [period], the global mean temperature seems to have risen by as much as 5-8 °C (9-14 °F) to an average temperature as high as 23 °C (73 °F), in contrast to the global average temperature of today at just under 15 °C (60 °F) (wikipedia.org)
About 66 to 100 million years ago
During the later portion of the Cretaceous … average global temperatures reached their highest level during the last ~200 million years (wikipedia.org)
About 100 million to 542 million years ago
[At this time, there might have been periods …] of fluctuating temperature between ice ages, such as the current age, and “climate optima”, similar to what occurred in the Cretaceous [which is outlined above … and] Roughly 4 such cycles have occurred during this time with an approximately 140 million year separation between climate optima.
What We Use To Determine Or Guess Earth’s Climate & Temperature From The Past
More modern devices and technology have been used to collect data on Earth’s temperature/climate in the last few hundred years.
Since around 1850 thermometers started to be used, and in more recent times, more advanced technology like satellites and balloons have been used.
Prior to 1850 however, direct measurements of Earth’s climate are not available
Instead, we rely on proxies and analysis of very old Earth material (like tree rings, ice cores, and deep sea sediments and geological records), along with fields of study like Paleoclimatology, to reconstruct or guess what the climate was like.
A list of the methods or data used to get an idea of Earth’s temperature at different times throughout history are:
– 1950’s to now
Satellites and balloons
– 1000 to 2000 years ago
Tree rings and ice cores, and indirect historical proxies (records and reports from humans at that time)
– 12,000 years ago
This time period might be studied by paleoclimatology
– 800,000 years ago
Although, with ice cores, large scale signals are clear, but specific detail might have interpretation issues
– Millions of years ago
Geologic evidence, such as deep sea sediment cores
Read more about these time periods and methodologies and data used to understand global temperature records throughout history at wikipedia.org
Uncertainty In Determining Earth’s Climate & Temperature History
The most recent climate records and direct measurements since around 1850 might contain more certainty to them.
Climate history from millions, or hundreds of millions of years ago (or more) especially might be seen as approximations only, and not definitive.
And, there might be a range of reasons that using ancient Earth data to interpret climate history has reliability or accuracy issues .
As a result, climate records might possess a level of uncertainty.
Below, we list some of the reasons for this potential uncertainty, such as:
– Temperature change evidence being sporadic and scattered
– There can be problems in interpreting detail in ice cores, and connecting variations
– There can be discrepancies in different reconstructions
– The combination of some records may not be valid
– Some temperatures records may be more qualitative than quantitative in nature
– Some evidence may be experimental in nature
– The best proxy records might contain few observations, and the spatial and temporal resolution of the resulting reconstructions is correspondingly coarse
– Geological evidence may involve much more speculation and approximation than some physical proxies
– Some ice core measurements can result in different interpretations than others depending on the procedure used
– Some isotopic data from the ocean is only up to 200 millions years only, with older sediments having various issues to consider
The full information on the above reasons includes …
‘The most detailed information [on global temperatures] exists since 1850, when methodical thermometer-based records began … (wikipedia.org)
Prior To 1850
– Geologic Temperature Records
With Geologic temperature records (such as deep sea sediments), sometimes scientists can only classify temperature fluctuations from certain time periods as ‘likely’, because ‘evidence of temperature changes and glaciation is usually too scattered and sporadic to draw firm conclusions’ (wikipedia.org)
‘[There can be a] discrepancy between the reconstructed geologic temperature record and the reconstructed amount of incoming solar radiation, or insolation over the past 800,000 years’ (wikipedia.org)
‘[The] Direct combination of [some] interpreted geological temperature records [are] not necessarily valid, nor is their combination with other more recent temperature records, which may use different definitions … [Instead, they may be used for] an overall perspective … even when imprecise’ (wikipedia.org)
– Ice Cores
When determining global temperature records for the last 800,000 years ago from ice cores:
‘… large-scale signals from the cores are clear, [but] there are problems interpreting the detail, and connecting the isotopic variation to the temperature signal’ (wikipedia.org)
Temperature estimates from oxygen isotope measurements on the north Greenland ice core … [can yield slightly different interpretations of temperatures depending on if simple procedures or more modern and complex procedures are used] (wikipedia.org)
– Proxy vs Observational Records
Even the best proxy records contain far fewer observations than the worst periods of the observational record, and the spatial and temporal resolution of the resulting reconstructions is correspondingly coarse (wikipedia.org)
– Physical Proxies vs Geological Records
‘A substantial achievement of the last 30 years of climate science has been the production of a large set of actual measurements of temperature history (from physical proxies), replacing much of the earlier geological induction (i.e. informed guesses) … Because many proxy temperature reconstructions indicate local, not global, temperature — or ocean, not air, temperature – substantial approximation may be involved in deriving these global temperature estimates’ (wikipedia.org)
– Human Records vs Natural Proxies
‘[… human] records can be used to infer historical temperatures, but generally in a more qualitative manner than natural proxies’ (wikipedia.org)
‘… the deep marine record, the source of most isotopic data, exists only on oceanic plates, which are eventually subducted: the oldest remaining material isold. Older sediments are also more prone to corruption by diagenesis. Resolution and confidence in the data decrease over time.’ (wikipedia.org)
– Earth Temperatures In General
‘[Temperatures from 10 to 100 million years ago can be] … very approximate, and best viewed as a qualitative indication only’ (wikipedia.org)
[Determining Earth’s climate or temperatures from 1000’s of millions of years ago, or billions of years ago may have] … proposals [that] are poorly constrained by existing experimental evidence (wikipedia.org)
What About Abrupt Climate Change? What Is It?
Abrupt climate change is different to regular climate change.
The main difference is that:
– An abrupt climate change event happens suddenly and quickly (and usually unexpectedly) over the course of shorter timespans, like years or decades, or the course of a human lifetime
But, the timescales can also vary
– Regular climate change on the other hand happens gradually and more slowly over the course of longer timespans, like tens of thousands of years, millennia, or millions of years
ucsusa.org, wikipedia.org, and science.org.au explain abrupt climate change in more detail
What Causes Abrupt Climate Change Events, & What Events Might Precede Them?
Both wikipedia.org and ucsusa.org might indicate that abrupt climate change events are linked to changes or shifts in the ocean circulation pattern, known as thermohaline circulation
skepticalscience.com might indicate that abrupt climate change events are caused by large releases of greenhouse gases, and they also outline symptoms of those events
[A precursor to abrupt climate shifts is a sudden circulation shift]
[And, abrupt climate change is possibly the result of] … feedback loops within the climate system’ … [where a] warming event causes a change that ads to further warming
[The Younger Dryas abrupt climate event from the past] and other abrupt events have been linked to changes in an ocean circulation pattern known as thermohaline circulation [and …] Past changes in thermohaline circulation have occurred during periods of relatively rapid climate change, such as transitions in and out of glaciations [or rapid warming like we are seeing today, however,] a shutdown of thermohaline circulation is unlikely to occur in the next century
[ucsusa.org provides a more thorough explanation of how this circulation change might have happened in past abrupt events in their report]
… [in the past] when Earth’s temperature jumped rapidly …Those times were caused by large and rapid greenhouse gas emissions, just like humans are causing today.
[For example …] global warming 66 million years ago was due to catastrophic eruptions in India, which emitted a pulse of CO2 that sent global temperatures soaring by 7°C (13°F).
[Massive volcanic eruptions may have released these emissions in the past … but there are none] operating today, or anytime in the last 16 million years [i.e. today’s volcanoes aren’t capable of emitting this level of emissions]
The symptoms from those events (huge and rapid carbon emissions, a big rapid jump in global temperatures, rising sea levels, ocean acidification, widespread oxygen-starved zones in the oceans) are all happening today with human-caused climate change
[skepticalscience.com explain more about what causes rapid global warming in their report]
Potential Examples Of Past Abrupt Climate Change Events
Below are some examples of past abrupt climate change events, when they might have happened, how much and how quick the temperature changed, and other relevant details
During global events, over a short time span, temperatures may have jumped and warmed anywhere between 4 to 10 degrees celsius, or even cooled by 3 to 4 degrees celsius
There may have also been regional abrupt climate change events, which are different to global events
Past [abrupt climate change] events include the end of the Carboniferous Rainforest Collapse, Younger Dryas, Dansgaard-Oeschger events, Heinrich events and possibly also the Paleocene–Eocene Thermal Maximum.
Changes recorded in the climate of Greenland at the end of the Younger Dryas, as measured by ice-cores, imply a sudden warming of +10 °C (+18 °F) within a timescale of a few years [… whilst] Other abrupt changes are the +4 °C (+7.2 °F) on Greenland 11,270 years ago or the abrupt +6 °C (11 °F) warming 22,000 years ago on Antarctica.
By contrast, the Paleocene-Eocene thermal maximum may have initiated anywhere between a few decades and several thousand years.
[wikipedia.org has more details on these events in their report]
[An] abrupt climate change event [was] the Younger Dryas (~12,000 years ago), a period of abrupt cooling that interrupted a general warming trend as Earth emerged from the last Ice Age [… and during this] period, average summertime temperatures in New England cooled by about 5-7°F (3-4°C) (ucsusa.org)
… there have been several times in Earth’s past when Earth’s temperature jumped rapidly, in much the same way as they are doing today (skepticalscience.com)
… there is … evidence that some abrupt [climate] changes occurred, at least at regional scales.
For example, during the last ice age, temperatures in the North Atlantic region changed by 5°C or more over as little as a few decades, likely due to sudden collapses of Northern Hemisphere ice sheets or changes in ocean currents.
Potential Effects Of Past Abrupt Climate Change Events
Several reports provide information on what the impact or effects of abrupt climate change events might have been
Mass extinctions is a commonly listed effect
How Have Past Abrupt Climate Change Events Been Measured?
Ice cores, and also other proxy material have been used to get measurements or records of past sudden climate change events.
Changes recorded in the climate of Greenland at the end of the Younger Dryas [have been] measured by ice-cores … (wikipedia.org)
From ice cores, ocean sediments, tree rings, and other records of Earth’s past climate, scientists have found that changes in climate have occurred quickly in the past—over the course of a decade (ucsusa.org)
The Current Understanding Abrupt Climate Change, & Predicting Future Abrupt Climate Events
The current understanding of abrupt climate change might generally be poor
Therefore, data and reports on the topic might be considered speculative in nature (and not definitive)
We also may not be able to predict future abrupt climate events with any certainty, or model past abrupt climate shifts accurately or reliably
Understanding Abrupt Climate Change
Scientific understanding of abrupt climate change is generally poor (wikipedia.org)
Predicting Future Abrupt Climate Change Events, & Modelling Past Abrupt Climate Shifts
Climate models are unable yet to predict abrupt climate change events, or most of the past abrupt climate shifts (wikipedia.org)
Will Abrupt Climate Change Events Happen In The Future?
As mentioned above, there might be no way to reliably or accurately predict if abrupt climate change will happen in the future
However, several reports indicate that some factors might increase or decrease the likelihood that one happens.
And, as mentioned above in this guide, there may be certain events the precede an abrupt climate change event
Will Abrupt Climate Change Happen In The Future?
… abrupt climate change is not a certainty … (ucsusa.org)
Factors That May Increase The Probability Of Abrupt Climate Change
Factors that may increase the probability of abrupt climate change include higher magnitudes of global warming, warming that occurs more rapidly and warming that is sustained over longer time periods (wikipedia.org)
… human-caused climate change makes abrupt events more likely (ucsusa.org)
Factors That May Reduce The Likelihood Of Abrupt Climate Change
We can slow down global warming and reduce the likelihood of future abrupt climate changes by reducing our emissions of heat-trapping gases (ucsusa.org)
Factors That Impact & Drive Earth’s Climate At Any One Time
You can read more in this guide about the factors that night influence a change in the Earth’s climate.
12. Various ‘Better Meets Reality’ guides
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