1.6 Climates have always changed

The Earth’s climate system is chaotic in the sense that it is continuously changing. Temperature on our planet has changed much and quickly before. These changes can be global or regional: a temperature increase in the northern hemisphere can have had a corresponding lower temperature or no temperature change in the southern part of the world. A “little ice age” in the area around the North Atlantic, has not necessarily affected other regions of the world. A warm ‘bronze age’ in Northern Europe 5000 years ago did not necessarily change global mean temperatures much: an extra tilting angle of the polar axis would entail a warmer north but a colder south. As a rule, solar forcing, negative or positive, has been the main driving or radiative forcing agent for significant climate change throughout the times. Albedo and the chemical composition of the atmosphere have been feedback mechanisms, enhancing the solar forcing either way.

Most researchers think that the temperature rise during the first part of last century was connected to increased solar radiation, and some voice the opinion that at least parts of the temperature rise the last decades also has been caused by increased solar activity. However, according to the UN Panel of Climate Change (IPCC), it is unlikely that the temperature rise during the last decades can be explained by increased solar activity alone.The last forty years, every decade has been warmer than the preceding decade.This in spite of that solar activity this period has been the lowest for hundred years except for a solar outburst in 1998.
In addition, large amounts of aerosols from coal fired power plants and increasing traffic in the air, on sea and land camouflage parts of the warming trend.

sunspots

Solar irradiance and sunspots p.12

https://skepticalscience.com/solar-activity-sunspots-global-warming.htm

Solar forcing
A change in the solar radiation having an effect on the earth’s climate is called “solar forcing”. When the solar radiation is less than usual, the forcing is said to be negative. When the sun warms the earth more than usual, the forcing is positive.
Solar forcing tends to vary in fairly regular cycles.

.
.Radiative forcing
Radiative forcing can in a simple way be defined as a force that changes the equilibrium of the energy budget in our climate system.
Solar activity, or rather the insolation, is the main radiative forcing factor. Insolation varies, and the solar forcing can be quite significant one year, down to “equilibrium”; i.e. no forcing the next.
.

Aerosols
Negative albedo forcing from particles (aerosols) in the air, e.g. from burning of fossil fuels, will last for some hours or days.
Sulphur aerosols from big volcanic eruptions may stay in the stratosphere for 1-4 years, having a significant cooling effect in that period.
While solar forcing tends to level out over time, the forcing from additional, anthropogenic greenhouse gases in the atmosphere will increase over time. Radiative or climate forcing is therefore often calculated over e.g. a 30 or a 100 year period.

radiative forcing

Graphic: IPCC (2013) The physical science  WG 1

Climate change due to changes in the atmospheric chemistry will therefore be more enduring than those caused by changes in solar forcing.
Whether the radiative forcing is caused by solar activity or changes in the atmospheric chemistry or not, there will be an impact on the third main factor with influence on the world’s climate: albedo.

A cold climate over a long period will increase the size of ice covers, entailing an increase in the albedo, meaning that more sunlight will be reflected and thus strengthen the cooling process. Increasing albedo means increasing negative radiative forcing.
Cooling activates feedback mechanisms enhancing the cooling, and vice versa: warming will activate feedback processes enhancing the warming.

In summary: any factor that changes the energy balance of our planet, either cooling or warming the average global temperature for a longer period of time, is a climate forcing factor. When more energy comes in than goes out, energy accumulates and our planet warms. When more energy leaves our planet than comes in, the global average temperature cools down.

energy balance.jpg

Graphic: IPCC (2013) The physical science  WG 1

 

By Roger. F. Olsen, Quora:

The weirdest part of the “climate has always changed” babble is it’s presented as some sort of revelation that scientists hadn’t considered.

And , no surprise, it’s the number 1 myth about climate change. https://skepticalscience.com/argument.php

 

Comparing old Earth to modern Earth is just not relevant.

Climate deniers make the same two mistakes every time they use this silly argument:

  1. TIMEFRAME.

Earth has always warmed and cooled naturally” is conflating things that happen over the span of hundreds of thousands or millions of years with something that is happening in less than 100 year.

Natural cycles and Axial tilt and orbit shape only matters over spans of 10 000 to 100 000 of thousands of years. Orbital forcings have been negative for over 6,000 years

And when was the last time the planet had nearly 8 billion people burning fossil fuels warming the planet out of its natural cycles?

Now write that 500 times.

TIMEFRAME TIMEFRAME TIMEFRAME TIMEFRAME TIMEFRAME..

2. The Post hoc ergo propter hoc fallacy:

“The Latin phrase “post hoc ergo propter hoc” means, literally, “after this therefore because of this.” The post hoc fallacy is committed when it is assumed that because one thing occurred after another, it must have occurred as a result of it. Mere temporal succession, however, does not entail causal succession. Just because one thing follows another does not mean that it was caused by it. This fallacy is closely related to the cum hoc fallacy.”

Now ask yourself this question?

Can a camp fire also cause a forest fire even if lightning strikes have done so since the dawn of time?

Comparing old Earth to modern Earth is just not relevant.

Some 500 million years ago, when the number of living things in the oceans exploded and creatures first stepped on land, the ancient atmosphere happened to be rich with about 7,000 ppm of carbon dioxide.

Earth was very different back then: the Sun was cooler, our planet was in a different phase of its orbital cycles, and the continents were lumped together differently forming a huge land mass over the South pole called Gondwana. Thus ocean currents were different to today. This also made it possible for higher amounts of ice on land. Sea levels were also higher. And the temperature 10 C warmer than today.

None of these realities are relevant today,

and,

The fact that CO2 levels and temperatures were higher millions of years ago is irrelevant to whether people living today will be negatively impacted by recent high levels.

because,

The effects of today’s RAPID global warming are felt by societies and existing ecosystems adapted to the Holocene climate in OUR TIME – NOT the climate and CO2 levels that existed hundreds of thousand or millions of years ago which gave ecosystems time to adapt.

Over the Earth’s history, there are times where atmospheric CO2 is higher than current levels. Intriguingly, the planet experienced widespread regions of glaciation during some of those periods. Does this contradict the warming effect of CO2?

No, for one simple reason. CO2 is not the only driver of climate. To understand past climate, we need to include other forcings that drive climate.

Before SUVs, volcanos and flood basalt events could release huge amounts of CO2.

Fossil algae reveal 500 million years of climate change | Geology Page

“The data show the present idea that rises in CO2-levels that used to take millions of years, are now happening in a century”

“In the past, when CO2 levels rose higher than they are today, it often happened over millions of years and the various forms of life on earth were able to evolve and adapt. But there were a number of times when CO2 levels and temperatures rose as quickly as they have risen in the last 100 years. These changes had profound consequences leading to mass extinctions. For example, 252 million years ago there was a rapid rise in CO2 due to a series of volcano eruptions, and global temperatures rose 11 deg. C wiping out 95% of all species on earth.

It used to be natural cycles and orbit shapes and axial tilt, but now humans are dwarfing the natural forcings.

We were in a cooling phase that was decreasing the global temperature by 0.1 C every 1,000 years. This stopped abruptly about 100 years ago when we started adding massive amounts of CO2 and other greenhouse gases to the atmosphere, causing a 1.15 C (2.07 F) per century increase.

Human caused climate change is a side effect of industrial capitalism. Industrialized nations were built with energy from cheap fossil fuels, and this released enormous amounts of greenhouse gasses into the atmosphere.

  • Now the changes are much faster than the natural forcings AND goes in the OPPOSITE direction to the cycles. Human caused climate changes is the abrupt u-turn in the OPPOSITE direction. If it was still a natural cycle, we should still be going slowly cooler down the “green” trendline towards the next ice age:
  • Global Climate changes in the past followed their natural cycles and were slow (with a few exceptions science knows about).
  • Here we see the moment when natural climate change became AGW! The moment climate was forced out of its Natural Milankovitch cycle to head in the opposite direction:
  • The climate hasn’t changed much since we settled into towns, invented plumbing, and started calling ourselves civilized.
  • Thus it’s dramatic how fast we left the stable temperatures that allowed the development of agriculture and human civilization to arise.

Read more:

 

Next

Home  
 Chapter 11     The natural greenhouse effect
  1.1  The science of the natural Greenhouse effect
  1.2  The Greenhouse Gases  (GHG)
  1.3   What causes climate change?
  1.4   Greenhouse effect on other Planets?
  1.5   Weather or Climate?
  1.6   Climates have always changed
   
 Chapter 22 Global Warming