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Evidence That Global Warming Is Being Caused by Humans

I have been studying the science of global warming with a passion since the late 1970s and earned a degree in Environmental Science in 1992.

This article will help you understand the ice age cycle and what's really causing temperatures to rise.

This article will help you understand the ice age cycle and what's really causing temperatures to rise.

Earth’s temperatures have warmed over the past century as carbon dioxide levels have increased. There is a strong indication that implicates mankind’s release of greenhouse gases into the atmosphere as being the primary cause of global warming.

Since there is a lot of noise and misinformation in the debate regarding what the cause of rising global temperatures is, it is best to take a broader view of the cause and effect of global warming. How do we know that mankind’s emissions of greenhouse gases are the cause of the recent global warming trend? The best indication that mankind is responsible for the current global warming trend is found by taking a broad look at where the recent global temperature rise fits into the natural glaciation (ice age) and warm period (interglacial) cycle that the Earth has been going through for millions of years.

Earth's Global Temperatures Over the Past 12,000 Years

During the current interglacial warm period, the global average atmospheric temperature of Earth peaked about 7,000 years ago, then commenced on a long gradual decline to cooler temperatures until very recently. Over the past 150 years global average

During the current interglacial warm period, the global average atmospheric temperature of Earth peaked about 7,000 years ago, then commenced on a long gradual decline to cooler temperatures until very recently. Over the past 150 years global average

Sun-Earth Cycles That Affect the Earth's Climate

Since the 1980s solar radiation from the Sun has decreased, yet global temperatures increased over this same time period.

Since the 1980s solar radiation from the Sun has decreased, yet global temperatures increased over this same time period.

Why Are Global Temperatures Warming When an Ice Age Should Be Approaching?

The historical global average atmospheric temperature record shown above has been compiled by an array of scientists that study Earth’s past global temperatures by analyzing ice sheet cores and other data. The temperature record indicates that the Earth should be heading into another ice age right now at a time when Earth’s temperatures are warming. The figure above shows the Earth’s global temperatures since it emerged from the last ice age and entered the current interglacial warm period, known as the Holocene epoch, about 11,000 years ago. As you can see, the global average atmospheric temperature of Earth peaked about 7,000 years ago and commenced a long gradual decline to cooler temperatures until they spiked higher in recent years to levels above the peak that occurred approximately 7,000 years ago.

An astronomer named Milutin Milankovitch from Serbia proposed in 1941 that ice ages are caused by changes in the Earth’s orbit around the Sun and its tilt in regards to the Sun. These changes occur in predictable cycles that when aligned correctly cause the amount of solar radiation reaching the Earth’s polar regions to diminish, which starts a new ice age cycle to commence. However, scientists determined that a lack of solar radiation was not enough to allow an ice age to progress beyond the initial stage. Scientists found that carbon dioxide levels had to reach a certain low level as ice formation during the initial cool down removed carbon dioxide from the atmosphere in order to kick the Earth’s cooling feedback loops and subsequent ice age into high gear. As more water was frozen into ice, more carbon dioxide was removed from the Earth’s atmosphere, causing further temperature drops and a feedback loop that continued the cooling until large ice sheets grew over many of the continents and a full ice age had taken hold of Earth.

What does the glaciation (ice age) cycle have to do with looking for evidence that mankind is the cause of the recent global warming that Earth has been experiencing? To answer this question, it is important to understand the natural length of the Earth’s natural glaciation (ice age) cycle. An ice age lasts approximately 100,000 to 120,000 years, while the much briefer inter-glacial (warm) periods last approximately 10,000 to 12,000 years. With this understanding and the fact that the last ice age ended about 12,000 years ago, the Earth should be starting a new ice age right about now. The figure above clearly shows global average atmospheric temperatures gradually sliding lower until they recently spiked higher.

What is the reason the Earth has broken its long-established ice age cycle and suddenly started warming when it appeared to be naturally ready to begin a new ice age? What is a variable that did not exist during prior interglacial periods? Mankind’s burning of fossil fuels and the subsequent increase in atmospheric carbon dioxide levels is the variable. Looking back at the geological record and taking into consideration the glaciation cycle initially driven by the Earth and the Sun's interaction, the global warming trend that has been evident for the past 150 years does not appear to be natural since the natural course in the Earth’s glaciation cycle is to be sliding into another ice age right now. This trend lower in temperatures has been halted and the climate has moved into a warming phase.

Global Temperature and Carbon Dioxide From 1880

This graph shows global temperatures and  carbon dioxide accelerating higher in tandem in recent years.

This graph shows global temperatures and carbon dioxide accelerating higher in tandem in recent years.

Is Global Warming a Bad Thing? A Little Bit No, But If Left Unchecked, It Will Be Very Bad

It can be argued that a little man-induced global warming is a good thing since a new ice age would be very problematic for the supply of food that mankind relies upon and for life on Earth, as currently habitable land areas would become covered with ice. However, global warming that occurs quickly will likely cause dire outcomes in the upcoming centuries for future generations of humans. Runaway global warming would cause sea levels to rise at an increasing rate, flooding the world’s population centers that are near sea-level and low-lying food-producing areas. Additionally, some of the current farmable lands would become arid and unfarmable in a world that warms by several degrees Celsius.

Is it too late to stop runaway global warming? Perhaps it is. Even if the entire world switched from carbon-based fuels to non-carbon based renewable energy next year, the buildup of carbon dioxide that has already occurred in the atmosphere would continue to increase global temperatures for many centuries into the future. It takes natural processes a long time to remove carbon dioxide from the atmosphere. Additionally, the warming of the Earth's atmosphere in the coming centuries will cause positive feedback loops that will increase the rate of global warming. Once the global temperature increases past a certain point, it will cause the release of large amounts of the potent greenhouse gas methane which is currently frozen in polar regions of the Earth and under ocean floors. If the Earth reaches the tipping point at which methane gas is liberated in increasingly large quantities from ice formations that it has been bound to for millions of years, global warming will enter a self-reinforcing positive feedback loop that will raise the average global temperature dramatically over time; a condition known as runaway warming.

Runaway Global Warming Will Reduce Useable Farmland

Some of the world's rich farmland areas will suffer prolonged droughts in a rapidly warming world.

Some of the world's rich farmland areas will suffer prolonged droughts in a rapidly warming world.

What’s Really Warming the Earth?

Addressing Global Warming

© 2019 John Coviello


John Coviello (author) from New Jersey on March 08, 2019:

Thank you Arthur for sharing your observations regarding how the climate change in recent decades has changed species habitat and growing patterns in your areas. Very interesting!

Eric Dierker from Spring Valley, CA. U.S.A. on March 07, 2019:

Arthur that is so interesting.

Arthur Russ from England on March 07, 2019:

Yep John, we’ve experienced what (as you say) “species habitat expansion towards the poles” in Britain at an ever increasing rate over the last 30 years due to our climate warming; for example:-

Britain had always been too cold for good quality wine until quite recently e.g. there were few vineyards in the UK prior to the 1980s because our climate was too cold; now with a warmer climate wine growing is flourishing in the UK, with there being now more than 450 vineyards in southern England producing good quality wine.

Climate change is good news for England's wine industry: https://youtu.be/gnbsHbYjLGk

Likewise, insects common in northern France are now appearing in southern England for the first time, while insects (including butterflies) that were common in southern England are migrating further north, displacing insects in the north of England that only survived in the colder climate of Northern England.

Also, fish and other marine life common in warmer waters further south, and until the last few years were never previously seen in British waters, are now becoming more common in the seas around Britain.

Likewise, annual migration patterns of some bird species are changing rapidly. UK Birds Species and Climate Change: https://youtu.be/umivQ4_pEEs

It’s not just animal and insect life; as a keen gardener, I can grow many more plants and flowers in my garden which now survives our warmer winters, that wouldn’t have done so in the colder British winters of just 20 years ago. The most striking difference of our winters, where I live, is that until the late 1980s we used to get up to 6 inches of snow every winter, now we almost never get any snow.

Also, the growing season in southern England has been significantly extended. 20 years ago, the growing season for summer crops in my back garden was from the beginning of April until mid-September. Now it’s from early March until late October. And some summer flowers in my garden, such as the half-hardy fuchsia, and marigolds, that used to die back by October, now often continues to flower in my garden until early January.

John Coviello (author) from New Jersey on March 07, 2019:

The serious scientific studies and literature have always been about CO2 accumulation, not thick grey fog or smog. I cover this in an article I published called The History of Global Warming and Origin of the Term Climate Changehttps://discover.hubpages.com/education/The-Origin...

As I said, there is a lot of noise in this whole Global Warming debate. Yes, the urban heat island effect is real, but it's been around for many decades and centuries, so it's baked into the numbers and has been for a long time at this point. We know the Earth is actually warming from secondary indicators, such as sea level rises (which are occurring at a faster rate over time), glacier retreats, and species habitat expansion towards the poles.

I think we actually have to start worrying about methane (CH4) that has been trapped in ice at the poles, in permafrost, and under the oceans for millions of years. Warming due to CO2 is the trigger that will potentially start a strong positive feedback loop as more CH4 is released and increases Earth's average temperature, even more, due to CH4 being introduced to the atmosphere, going round and round with additional releases of CH4. You can read more about this possible scenario in How Methane Gas Releases Due To Global Warming Could Cause Human Extinction https://discover.hubpages.com/education/How-Methan...

Regarding volcanoes. When large volcano eruptions occur they tend to cool the Earth's atmosphere and bring down temperatures for a few years. This has happened several times over the past 200 years, including back in the 1990s. This cooling is temporary and is due to ash and sulfur dioxide (SO2) emissions into the atmosphere that blocks the sun's rays. But, the effect only lasts one to three years as the ash and SO2 dissipates, and then the Earth's climate returns to being driven by other forcings such as CO2.

Eric Dierker from Spring Valley, CA. U.S.A. on March 06, 2019:

Bruce you just made me laugh. Not at you but at me. Last night my son and I (9) were going back and forth about Nitrogen, Co2, farting (methane - including cows), Carbon Monoxide, and all that fun stuff. We just shrugged and went out into our natural - for sure no chemical insecticide or weed killer, and breathed in the oxygen.

I am not clear on your notion that "soot" is invisible? But I would think that would block out the sun and make it colder - but then it may trap in the heat and make it warmer.

Arthur Russ from England on March 05, 2019:

Yep, I’m with you John. This is a pet subject of mine, one that I’ve kept a keen eye on for some years now.

As your analysis surmises, it may be too late! Albeit on a more positive note, virtually every country in the world is making an effort (including China) to transition from fossil fuels to renewable energy, with some doing better than others; but certainly all could do more.

Britain, as with most of Europe, has done its bit, and is on track to achieve its goal of being near carbon neutral by 2050 e.g. as well as quickly transitioning from fossil fuels to renewable energy, all fossil fuel cars in Britain will be banned by 2040 (2032 in Scotland). China and France will also ban these cars by 2040; although Norway will ban fossil fuel cars by 2025, and six other European countries are set to ban these cars by 2030.

The biggest success in the UK for transitioning to Renewable Energies is the wind farms. The first offshore wind farm in UK became operational in 2000, albeit it only consisted of just 11 wind turbines with a total capacity of only 4 MW (megawatts).

But great strides have been made since then. For example, last year 3 offshore wind farms became operational in the UK, with a combined total of 305 wind turbines, generating a total capacity of 1.7 GW (gigawatts), including the Walney wind farm extension:-

Walney Extension – the world’s largest offshore wind farm in 2018: https://youtu.be/rbnlJOEQ9Hc

As of end of last year there were a total of 9,391 wind turbines with a total installed capacity of over 20.5 GW; 12.6 GW of onshore capacity and 7.9 GW of offshore capacity; which accounts for over 25% of electricity generated in the UK. The latest offshore wind farm to generate electricity in the UK (now the world’s largest wind farm) went live in February 2019, generating 1.2 GW initially, but will eventually be generating 6 GW on completion.

At the end of last year 50.6% of the UK’s electricity needs where met from renewable sources; wind, Bio, Solar and Hydro. Burning coal now just 2% of the UK’s energy mix, with the last coal fire power station scheduled due to close in 2025; in contrast, back in 1990, 67% of Britain’s electricity came from coal, this had dropped to 22% by 2016, and to 2% last year and will be 0% by 2025.

The rest of Europe is following a similar pattern to the UK of switching from fossil fuels to renewables; as is China. To their credit, China is installing solar and wind farms at a far faster rate than any other country in the world; but their two main problems are that:-

i. Coming from a non-industrialised nation that rapidly industrialising as they make the switch over fossil fuels to renewable energy they are still heavily dependent on coal (in the interim), and

ii. With such a big population (1.4 billion), they consume a lot of electricity; albeit, they actually produce far less carbon dioxide per head of population than the USA.

Nitika Mehra from Delhi on March 05, 2019:


Bruce Deitrick Price from Virginia Beach, Va. on March 05, 2019:

40 years ago, the mechanism which caused higher temperatures was clear to everyone. Various emissions from cars and factories created a thick gray fog which TRAPPED heat. Thus the phrase "greenhouse gases."

But then someone noticed the obvious: this fog-layer would block out the sunlight, causing lower temperatures.

The global warming theorists dealt with this paradox by changing around vocabulary. There was no more mention of greenhouse gases. All emphasis was on Co2. This was certainly a component of industrial emissions, etc. But Co2 is a TRACE element and invisible.

The big question remains: how exactly is the temperature made to rise? What is the mechanism?

This article seems to deal in sleight-of-hand. Temperatures, we are told, are rising. There is more Co2 in the world. Ergo, one must be causing the other. But how? And keep in mind we do not even know for sure that temperatures are rising.

Decades ago, I could easily imagine the mechanism by which industrial smoke could trap heat. But now I can't put it together in my mind. Co2 is presented as something like a bad supernatural power. Invisible. But just by being there, it can warm up the world.

Also, don't forget that Co2 feeds plants and makes them big. The more Co2, the bigger the plants. The plants in turn shield the ground from solar heat.

(As for higher temperatures, many of the apparent increases are caused by the "heat island effect." That is, most of the weather stations are in airports or near cities. They are predictably hotter and they're artificially driving up the records. To get real temperature readings, you have to go 20 miles away from the old weather stations. The notion that we have reliable records going back centuries is an obvious lie and for me tends to discredit the whole theory.)

Liz Westwood from UK on March 05, 2019:

This is a very topical article. I feel that the decisions we make now will have implications for the generations of the future.

Eric Dierker from Spring Valley, CA. U.S.A. on March 05, 2019:

Interesting. I thought that volcanic activity put off more carbon in a year than man has ever done. I also thought that the north passage near the Arctic was a normal concept long before human fossil fuel use.

My home's footprint is as near zero as possible. That just makes sense. We only use heat for one hour a day and never air conditioning and drive very little. We cultivate plants that are good.

India and China bother me. But I understand it.

Sue Pratt from New Orleans on March 04, 2019:

Thanks for the science/facts. It's a very well-written article. We ignore the warnings at our children's peril.

Carol Rafferty on March 04, 2019:

As far as I'm concerned mother nature is going off her rocker. She has having plenty of help though MAN!! Man has a way of toying with everything & making matters worse. Chem trails, I'm just thrilled!!!

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