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Sunday, September 13, 2026

About how much has the Earth's surface warmed

While we remain in an "Ice Age," we are in an interglacial warming period and have been coming out of serious ice for about the last ten thousand years, indicating some steady warming? Nevertheless, the recent warming indicates something new that wasn

Yes, that's essentially the key point.

We are indeed still in a geologic ice age. Geologists use "ice age" to mean a period when permanent ice sheets exist somewhere on Earth. Antarctica and Greenland still have them, so the present ice age began about 34 million years ago and continues today.

Within an ice age there are glacial and interglacial phases. We are living in the current interglacial, the Holocene, which began about 11,700 years ago when the great Northern Hemisphere ice sheets retreated.

The interesting wrinkle is that there is a scientific debate about what happened after that initial warming. There is no dispute that Earth warmed dramatically from the Last Glacial Maximum (about 20,000 years ago) until the early Holocene. The debate is whether global average temperature then:

  1. Peaked roughly 6,000–8,000 years ago and slowly cooled until the Industrial Revolution, or
  2. Continued a very slight long-term warming until recent centuries.

Many proxy reconstructions show a gentle cooling trend of roughly half a degree Celsius from the mid-Holocene to the 1800s, culminating in the Little Ice Age. The IPCC concludes with high confidence that global temperatures generally decreased after about 6,000 years ago and that this trend reversed in the nineteenth century.

So the picture many climatologists would draw is:

  • Rapid natural warming as the last ice age ended.
  • Several thousand years of relatively stable climate, perhaps with a slight cooling tendency.
  • Roman Warm Period, Medieval Warm Period, Little Ice Age, and other smaller fluctuations.
  • Then, beginning around the mid-1800s, a sharp warming that differs from the preceding trend.

What makes modern warming noteworthy is not merely that temperatures are rising. Temperatures have risen naturally many times in Earth's history. Rather, the notable features are:

  • The warming occurs while orbital cycles alone would not be expected to produce such a rapid increase. In fact, many reconstructions suggest the long-term natural tendency over the last several thousand years was toward slight cooling.
  • The rate of warming since about 1950 is exceptionally rapid. The IPCC states that the observed warming rate since around 1950 is unprecedented for any 50-year period in at least the last 2,000 years.
  • Atmospheric CO₂ has risen from roughly 280 ppm before industrialization to over 420 ppm today, providing a physically understood mechanism for additional warming.

If you were standing in Europe 15,000 years ago watching mile-thick ice retreat northward, you would certainly say, "The Earth is warming." And you would be right. But the mainstream scientific view is that the warming since the nineteenth century is not simply a continuation of that deglaciation. It is occurring after the deglaciation was essentially complete and after thousands of years of comparatively small temperature changes.

As an anthropologist, you might appreciate the scale: agriculture, cities, empires, Buddhism, Christianity, Islam, the Roman Empire, the Khmer Empire, and the entire span of recorded history all developed during a climatic interval in which global temperature probably varied by less than about a degree Celsius until the modern era. The recent warming stands out because it is large compared with the climatic range experienced by most human civilizations.


So it seems recent warming cannot be attributed to natural climate change, but to the industrial revolution, in particular the burning of fossil fuels, first coal and later oil products.

That is the conclusion reached by the overwhelming majority of climate scientists today, yes.

The important distinction is between "natural climate change exists" and "natural climate change explains the recent warming." The first statement is unquestionably true. Earth's climate has always changed. Ice ages came and went long before humans burned coal. The Roman Warm Period, Medieval Warm Period, and Little Ice Age all occurred without factories or automobiles.

The second statement is where the evidence points in a different direction. Modern attribution studies ask: If we include only natural factors such as solar variability, volcanic activity, and internal climate fluctuations, do we get the warming that was observed? The answer is no. The observed warming can be reproduced only when human influences—especially greenhouse gases from fossil fuel combustion—are included.

One of the strongest pieces of evidence is that scientists can estimate the separate contributions:

  • Human-caused greenhouse gases produced a substantial warming effect.
  • Human-produced aerosols (pollution particles, especially from coal burning) produced some cooling that partially masked that warming.
  • Natural influences since the late 19th century contributed very little net change, roughly around zero globally.

The IPCC's current position is unusually direct for a scientific body: it is "unequivocal" that human influence has warmed the atmosphere, ocean, and land, and human activities, principally greenhouse-gas emissions, have caused the observed global warming.

Historically, the sequence you describe is essentially correct:

  1. Coal use expands in Britain and later Europe and North America during the Industrial Revolution.
  2. Atmospheric CO₂ begins rising measurably.
  3. Oil and natural gas use accelerate in the 20th century.
  4. CO₂, methane, and other greenhouse gases rise far beyond pre-industrial levels.
  5. Global temperatures rise, especially after about 1950.

There are still scientific discussions about details—how sensitive the climate is, how regional rainfall patterns will change, how much warming is already "locked in," and so forth. But the basic attribution of most recent warming to human activity is no longer one of the major disputed questions within climate science.

As a historical observation, it is rather remarkable. Humans spent hundreds of thousands of years adapting to climate. Then, within roughly two centuries, a species that learned to dig up ancient carbon deposits and burn them became a significant climate driver itself. From the perspective of a future geologist looking at sediment layers, the Industrial Revolution may stand out as one of those sharp turning points that mark the beginning of a distinct chapter in Earth's history.

 

 

Why is that such a bad thing? After all, more land to the north becomes arable, Arctic seas open?

That's a fair question, and climate scientists would generally answer: it isn't all bad. There are genuine benefits. The issue is whether the benefits outweigh the costs and where those benefits and costs occur.

For example, you mention two real advantages:

  • Longer growing seasons in places like Alaska, northern Canada, Scandinavia, and parts of Siberia.
  • More open Arctic waters, potentially shortening shipping routes between Europe and Asia.

Climate researchers acknowledge both of those. In fact, some Arctic regions are already seeing increased agricultural opportunities and longer frost-free seasons.

The problem is that the benefits are unevenly distributed.

A farmer in northern Manitoba may gain growing days, while a farmer in India, Cambodia, or parts of Africa may experience more frequent heat stress and water problems. Global food production depends heavily on already-warm regions where crops can be pushed beyond their optimum temperatures.

Another issue is that climate is not just temperature. If warming merely meant "every place becomes a little warmer," adaptation would often be straightforward. But warming can also alter rainfall patterns, snowpack, river flows, drought frequency, wildfire conditions, and coastal flooding risks.

The Arctic itself illustrates the tradeoff nicely. More shipping opportunities and economic activity are expected. At the same time, permafrost thaw damages roads, buildings, pipelines, and other infrastructure that were built on permanently frozen ground.

There's also a time-scale issue. Human civilization developed during a relatively stable climatic period. Farmers, cities, reservoirs, ports, and transportation systems were built around historical conditions. A climate that changes over centuries is easier to adapt to than one that changes substantially within a few generations.

As an anthropologist, you might recognize a parallel. Humans can adapt to deserts, rain forests, tundra, and tropical islands. The challenge is often not the environment itself but the transition from one environment to another while millions or billions of people already have investments, farms, and cities in place.

There is also a philosophical point that sometimes gets lost in public discussion. A warmer world is not necessarily a worse planet in some absolute sense. During parts of Earth's history, the planet was much warmer and life flourished. The concern is more pragmatic: Is a rapid warming trend beneficial or harmful to the particular civilization we have built where we have built it?

Reasonable people can disagree about the magnitude of the risks, the economics of mitigation, or how much adaptation is preferable to emissions reduction. But the mainstream scientific concern is not that warming produces no benefits. It is that the expected benefits are outweighed globally by the expected disruptions and costs as warming increases.

And there is one historical irony here. If you had asked a farmer in Sweden in 1700 whether a slightly warmer climate sounded attractive, he might well have said yes. If you ask a farmer in already-hot tropical lowlands the same question, you may get a very different answer. Geography has a lot to do with how people perceive climate change.

 

I tend to the view that the biggest problem is that global warming, particularly rapid warming, is more difficult to make adjustments and evolve with and that sea level increases in generational terms.

 

 

That's actually quite close to how many climate economists and adaptation specialists frame it.

The Earth itself is not in danger from a 1–3°C warming. Nor is life in general. Earth has experienced much larger climatic swings. The question is how comfortably human societies can adapt to the pace of change.

Sea level rise is a good example. If the oceans were destined to rise 2 meters but took 5,000 years to do so, most human societies would adapt almost invisibly. Harbors would be rebuilt, settlements would migrate inland, and maps would gradually change. It would be more of a historical process than a crisis.

The difficulty comes when changes occur over decades rather than millennia. A coastal city may have trillions of dollars invested in infrastructure built for conditions that existed when it was designed. Moving a village is easy; moving Bangkok, Shanghai, Miami, Rotterdam, or Alexandria is not.

Your point about evolution is also important. Natural selection can accommodate remarkable environmental changes, but it works over generations. Many species can handle climate shifts if they occur slowly enough for migration, adaptation, or genetic change. Rapid shifts are harder because suitable habitats may move faster than populations can follow.

Historically, humans have often proven surprisingly adaptable. The Dutch built dikes. People in arid regions developed irrigation. Air conditioning transformed settlement patterns in hot climates. New crop varieties appear. So there is a strong argument that humanity will adapt to a considerable amount of warming.

The debate tends to be over cost and disruption, not over whether adaptation is possible at all. For example:

  • A farmer changing crops is adaptation.
  • A city raising seawalls is adaptation.
  • Relocating millions of people from low-lying deltas is adaptation.

All are possible, but some are much more expensive and socially disruptive than others.

One thing anthropologists and historians often notice is that civilizations generally do best during periods of relatively predictable conditions. Sudden changes—whether climatic, economic, political, or epidemiological—tend to be harder to manage than the absolute state itself. A society can flourish in a cold climate or a hot climate if it has time to organize around it.

So your emphasis on rate of change rather than simply temperature is very much in line with a major strand of thinking in climate science and environmental history. A warmer world is not automatically a catastrophe; a rapidly changing world is often a more demanding one for both human institutions and natural ecosystems.

 

 

So a lot of cost and suffering might be avoided if we slow it down.

Exactly. That's probably the strongest version of the argument for mitigation: the objective needn't be to prevent every degree of warming; it can be to buy humanity—and ecosystems—more time to adjust.

If warming were spread over several centuries rather than concentrated into a century or two, several things become easier:

  • Coastal adaptation: seawalls, drainage, ports, and eventually relocation can be planned and rebuilt gradually rather than in emergency mode.

  • Agriculture: crops, livestock, irrigation, and farming regions can change progressively.

  • Ecosystems: species have more opportunity to migrate and adapt rather than suddenly finding their climate envelope somewhere hundreds of kilometers away.

  • Infrastructure: buildings and transportation systems can be replaced at the end of their normal lives instead of being abandoned prematurely.

  • Human migration: people can move in response to changing conditions rather than being forced out by abrupt disasters.

  • Technology: we have more time for better cooling, water management, crop breeding, energy systems, and whatever solutions haven't been invented yet.

And there's a particularly important point in your formulation: slowing warming doesn't require knowing exactly what the optimum future temperature is. It preserves options. If the eventual answer turns out to be "a warmer Earth isn't nearly as bad as we feared," having warmed slowly still bought us adaptation time. If the damages turn out to be worse, slowing it bought us even more valuable time.

There is also an economic wrinkle. We shouldn't compare doing something about warming with doing nothing forever. The sensible comparison is between different trajectories: rapid warming, slower warming, and the costs of reducing emissions versus the costs of adapting to additional warming.

So I think your formulation is rather more defensible than the simplistic "global warming is bad, therefore stop it" formulation. The practical question is:

How much warming can we tolerate, at what rate, and what is the cheapest way of giving ourselves enough time to adapt?

That's a much more interesting—and much less apocalyptic—question.


Well a lot of warming and sea level rise is now locked in, so the issues are planning for it and how much and how fast.

Yes. That's a much more useful way to frame the problem.

Some additional warming and sea-level rise are effectively committed, because the climate system responds slowly to greenhouse gases already emitted. But "locked in" doesn't mean that the future is predetermined. There is a large difference between, say, 1.5°C, 2°C, 3°C, or more, and the timing matters enormously.

Sea level is particularly slow. Even if atmospheric warming stopped, oceans would continue to expand thermally and ice sheets would continue responding for a long time. So coastal planning has to think in terms of decades and centuries, not next year's weather.

That makes the sensible policy mix something like:

1. Mitigate what is reasonably economical.
Every fraction of a degree avoided is less adaptation required.

2. Adapt to the warming that is coming.
Don't build a new coastal development today on the assumption that the 20th-century shoreline is permanent.

3. Plan for several plausible futures rather than pretending we know the exact one.
A seawall designed for a particular sea level in 2100 is a rather different proposition from designing a city so that the seawall can be raised another meter later.

4. Keep adaptation options open.
That may ultimately be more valuable than trying to predict the precise climate a century from now.

And this gets back to your earlier point about rate. Suppose two worlds eventually reach the same temperature, but one takes 150 years and the other takes 500. The second gives coastal cities, farmers, ecosystems, engineers, governments, and populations vastly more time to respond.

There's a nice distinction here between climate change as a physical phenomenon and climate change as a human problem. The planet can accommodate quite extraordinary changes. We have to accommodate them while maintaining billions of people's homes, food supplies, infrastructure and institutions.

So I'd put your position this way: the question is no longer simply whether warming will happen, but how much, how rapidly, and how intelligently we respond to the trajectory we've already set in motion.

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