Discussion with ChatGPT on global sea level rise

posted 13 days ago by PhDinNY 13 days ago by PhDinNY +29 / -0

This is a little long, and only for those who want to learn a little more about global sea level rise. I have long contended that the "man-made climate change" propaganda is easily busted when viewing global sea-level rise. If there was a significant increase in the rate of global warming, presumably due to human activities, there would be a corresponding increase in the rate of global sea level rise. There has not been such an increase, UNLESS you use the satellite data that has only been collected for the past 30 years or so. The text below is my discussion with the chatGPT AI on this discrepancy.

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– PhDinNY [S] 2 points 13 days ago +2 / -0

what was the mean global rate of sea level rise between 1970 and 2020 ChatGPT said: ChatGPT Between 1970 and 2020, the mean global rate of sea-level rise was approximately 3.3 millimeters per year. This rate has been derived from satellite measurements and tide gauge data, and it reflects a steady increase due to melting ice sheets, glaciers, and the thermal expansion of seawater as it warms.

To put it into context:

From 1901 to 2020, sea levels rose by about 8–9 inches (21–24 centimeters) globally. The rate of sea-level rise has accelerated in recent decades, with the 3.3 mm/year average rate in the latter part of the 20th century being faster than earlier periods. Sea-level rise is driven by two main processes:

Thermal expansion: As ocean water warms, it expands. Ice melting: The melting of glaciers and ice sheets contributes additional water to the oceans.

You said: what was the mean global rate of sea-level rise between 1920 and 1970 ChatGPT said: ChatGPT Between 1920 and 1970, the mean global rate of sea-level rise was approximately 1.2 to 1.4 millimeters per year. This period saw a slower rate of sea-level rise compared to the rates observed in the latter part of the 20th century, reflecting changes in climate and ice melt processes over time.

Context: Prior to 1970, the rate of sea-level rise was relatively steady but lower than the 3.3 mm/year observed between 1970 and 2020. This slower rate was primarily driven by slower rates of ice melting and a smaller amount of thermal expansion. The acceleration of sea-level rise in the latter half of the 20th century is largely attributed to the increased rate of ice melt from glaciers and ice sheets and the warming of ocean waters due to global warming.

You said: what was the mean global rate of sea-level rise between 1870 and 1920 ChatGPT said: ChatGPT Between 1870 and 1920, the mean global rate of sea-level rise was approximately 0.5 to 0.8 millimeters per year. This period corresponds to the early stages of industrialization and the beginning of noticeable global warming trends, though the rate was much slower compared to later decades.

Context: Sea-level rise during this period was primarily influenced by thermal expansion as oceans began to absorb heat from rising global temperatures and by small amounts of glacier melting. The rate remained relatively stable and low compared to the accelerated sea-level rise observed from the mid-20th century onward. These estimates are based on tide gauge data and provide a baseline for comparing changes in sea-level rise rates as global warming has intensified over time.

You said: how do you explain the higher than present sea levels during the mid-Holocene period? ChatGPT said: ChatGPT During the mid-Holocene period (approximately 6,000 to 9,000 years ago), sea levels were higher than present-day levels by about 1 to 2 meters. This can be explained by a combination of factors related to Earth's climate, ice sheet dynamics, and geological processes at the time:

Warmer Global Climate The mid-Holocene was characterized by relatively warm global temperatures compared to today, driven by natural variations in Earth's orbit (Milankovitch cycles) and feedbacks within the climate system. Warmer temperatures caused melting of ice sheets and glaciers, contributing additional water to the oceans.
Ice Sheet Melting Ice sheets and glaciers were smaller than their peak during the Last Glacial Maximum (approximately 20,000 years ago), but still contributed significantly to sea-level rise. Melting from the Greenland Ice Sheet, Antarctic Ice Sheet, and mountain glaciers resulted in substantial ocean volume increases.
Thermal Expansion of Seawater The warming of ocean waters during this period caused thermal expansion, a process in which seawater expands as it warms, contributing to higher sea levels.
Geological Adjustments (Isostatic Rebound) During and after the last glaciation, large ice sheets covered much of North America and Eurasia. When these ice sheets retreated, the Earth's crust was rebounding, causing local shifts in sea level. This process can lead to regional variations in sea-level rise but contributed to the overall higher sea levels globally during the mid-Holocene.
Sea-Level Stabilization During the mid-Holocene, sea levels were in a state of stabilization, as the ice sheets had largely retreated from their maximum extent, and other feedbacks between climate and ocean systems were balancing. In summary, the higher sea levels during the mid-Holocene were driven by melting ice, thermal expansion of seawater due to higher global temperatures, and geological processes related to ice retreat and crustal adjustments. These natural processes led to a period of elevated sea levels, peaking before the climate system transitioned to the present-day equilibrium state.

You said: Since you clarified that the higher sea levels during the mid-Holocene period were caused by natural factors, why do you believe any present increase in the rate of global sea level rise is caused by human activities? ChatGPT said: ChatGPT That's an excellent question and highlights an important distinction between natural processes and anthropogenic (human-induced) influences on sea-level rise. While natural factors like orbital changes, glacial melting, and thermal expansion have influenced sea levels throughout Earth's history (such as during the mid-Holocene), the rapid acceleration of sea-level rise observed in recent decades is primarily attributed to human activities. Here's why:

The Rate of Change Is Unprecedented The current rate of sea-level rise (about 3.3 mm/year from 1970 to 2020) is significantly faster than any natural variation observed over the past 10,000 years. The mid-Holocene rise was gradual and tied to natural climate variations, while the recent rise is driven by a sudden and large increase in greenhouse gas emissions and rapid warming.
The Role of Greenhouse Gas Emissions Human activities like burning fossil fuels, deforestation, and industrial processes have led to increased atmospheric concentrations of CO2 and other greenhouse gases. These gases trap heat in Earth's atmosphere (the "greenhouse effect"), leading to global warming that directly causes ice melting and thermal expansion.
Accelerated Ice Sheet and Glacier Melting While ice melting has occurred naturally in Earth's history, the rates at which glaciers and ice sheets are melting today are far faster than natural variability would predict. Studies show that Greenland and Antarctica ice sheets are losing ice at accelerating rates, directly linked to warming ocean and atmospheric temperatures driven by human activity.
Thermal Expansion from Rapid Ocean Warming The oceans absorb over 90% of the excess heat from global warming, leading to thermal expansion—seawater expands as it warms. The observed warming trend of the ocean is largely the result of human-caused emissions, not natural processes.
Distinguishing Human Influence from Natural Cycles While natural cycles can cause sea-level changes over geological timescales, modern sea-level changes are occurring too quickly to be explained solely by natural processes. Climate models and observational data clearly link recent trends to human emissions. Climate science uses statistical models to compare observed patterns against both natural variability and human-induced scenarios. The evidence consistently points toward anthropogenic drivers. In Summary: The mid-Holocene higher sea levels were driven by natural processes like orbital changes, ice melt, and sea-level stabilization at that time. However, the current rate of sea-level rise (and its acceleration) is fundamentally different because it aligns with human activities—namely greenhouse gas emissions, fossil fuel use, deforestation, and other industrial processes.

The scientific consensus is that the recent, accelerated sea-level rise is largely anthropogenic because it coincides with rapid industrialization and its environmental effects, not natural climate cycles alone. The data from satellite observations, tide gauges, and climate models all support this conclusion.

You said: if the present rate of global sea level rise is significantly higher than throughout the 20th century, why would the areas of islands increase, as documented in https://www.tandfonline.com/doi/pdf/10.1080/17538947.2024.2329816 ChatGPT said: ChatGPT The observation that island areas are increasing in some cases despite the present rate of sea-level rise being higher than throughout much of the 20th century can be explained by a combination of natural processes and sediment dynamics. This phenomenon has been documented in studies like the one you referenced, and it reveals that local processes can counteract the effects of global sea-level rise in specific regions. Here’s why this might occur:

Sediment Redistribution and Accretion Many small islands, particularly those in river delta regions or coral atolls, gain land through natural sediment deposition. This occurs as sediments transported by ocean currents, waves, or river discharge are deposited on islands or coastal areas. This sedimentation can lead to island growth even as sea levels rise. Wave action and currents can transport sediment onto islands, reinforcing their size and contributing to land accretion.
Coral Reef Formation and Growth Coral reefs can grow and contribute to island formation or expansion, especially in atoll systems, where the islands are dependent on coral building processes. As long as coral reefs can keep up with sea-level rise by growing vertically, they can maintain or even increase their size.
Human-Managed Interventions In some places, engineering projects such as coastal restoration efforts, dredging, or sediment reallocation, are intentionally increasing island areas. These human efforts can mimic natural processes by importing sediment or reinforcing shorelines to maintain land despite rising seas.
Sea-Level Rise Is Not Uniform Everywhere Sea-level changes are not uniform globally. Regional variations in sea-level rise occur due to factors like ocean currents, glacial isostatic adjustment (rebound effects), gravitational effects from melting ice, and regional subsidence. In some areas, the local rate of sea-level rise may be slower than the global average, allowing natural processes like sediment deposition to outpace rising water levels.
Coastal and Geomorphic Processes Processes like erosion, sediment transport, and wave action can lead to dynamic changes in island size. While sea-level rise can lead to inundation in some areas, sediment dynamics can lead to net land gain in others. Key Insight: The phenomenon of islands expanding or maintaining their size in the face of sea-level rise does not mean that sea-level rise is not a threat. Instead, it highlights the complex interaction between natural sediment processes, ocean dynamics, and human interventions. While some islands may experience localized growth through these processes, many low-lying islands are highly vulnerable to sea-level rise, especially due to coastal inundation, storm surges, and saltwater intrusion.

The observed growth in island area in specific locations should therefore be understood within this context: it is a localized phenomenon driven by sediment dynamics and natural processes, not a counter to the global trend of sea-level rise.

You said: if only the global network of tide gages are used for data analysis, what is the rate of global sea level rise during the past fifty years ChatGPT said: ChatGPT When analyzing sea-level data using only tide gauges, the rate of global sea-level rise over the past 50 years (from approximately 1970 to 2020) is estimated to be around 1.5 to 2 mm per year.

Comparison to Satellite Data: Tide gauge data alone tend to show slightly lower rates of sea-level rise compared to satellite altimetry measure

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– PhDinNY [S] 1 point 13 days ago +1 / -0

if only the global network of tide gages are used for data analysis, what is the rate of global sea level rise during the past fifty years ChatGPT said: ChatGPT When analyzing sea-level data using only tide gauges, the rate of global sea-level rise over the past 50 years (from approximately 1970 to 2020) is estimated to be around 1.5 to 2 mm per year.

Comparison to Satellite Data: Tide gauge data alone tend to show slightly lower rates of sea-level rise compared to satellite altimetry measurements, which indicate a rate of about 3.3 mm per year over the same period. This discrepancy occurs because tide gauges are limited by their spatial distribution and only measure changes at specific coastal locations rather than offering comprehensive global coverage. Reasons for Differences: Geographic Coverage: Tide gauges are mostly concentrated near coastal areas and may miss regional ocean dynamics that affect global averages. Ocean Currents & Regional Variability: Local processes such as ocean circulation patterns, land subsidence, or glacial adjustments may affect tide gauge readings. Instrumental Gaps: Tide gauges have a smaller observational network and lack the comprehensive global coverage that satellites provide. Conclusion: Using only tide gauges, the global sea-level rise rate over the past 50 years is roughly 1.5–2 mm/year, whereas satellite observations show a faster rate of 3.3 mm/year due to the broader spatial range and sensitivity of satellite measurements.

You said: Satellite altimeter data is not reliable for any measurement less than 5 cm. How can instruments accurate to only 5cm be used to measure processes that can only be measured in millimeters. ChatGPT said: ChatGPT Your observation about the limitations of satellite altimetry is accurate—satellite altimeters have a vertical measurement accuracy of a few centimeters, typically 2–5 cm, which can raise concerns when interpreting very small changes like millimeters of sea-level rise. However, satellite altimeters are still highly reliable for monitoring sea-level trends over time and large spatial scales because they measure global patterns and temporal changes rather than small, localized variations.

Here’s how satellite altimeter data can be used to infer millimeter-scale processes over time:

Long-Term Trends vs. Instantaneous Changes While the accuracy of individual measurements might be in the centimeter range, long-term trends over decades are much more reliable because small variations average out over time. Sea-level trends are identified by comparing changes in sea level across many observations over many years, not focusing on instantaneous values.
Comparative Global Patterns Satellite altimetry relies on monitoring relative differences in sea level across different regions (spatial comparisons) rather than absolute measurements. Changes like global sea-level rise affect large geographic areas uniformly, allowing altimeters to pick up these signals with greater certainty. Even if a single millimeter change at a point isn't distinguishable, the consistent rise across global patterns (over many regions and time) can be robustly identified.
Statistical Approaches Sea-level rise data relies on statistical averaging over long periods. Statistical methods can extract signals from noisy data by examining sea-level changes over time across spatially distributed altimeter observations. These statistical techniques are sensitive enough to detect small signals like millimeters of global sea-level rise by reducing the "noise" in individual measurements.
Combination with Tide Gauges Satellite altimetry data is often combined with tide gauge observations, which can measure local sea-level changes with millimeter-level precision at specific points. When combined, satellite altimeters provide broader spatial coverage and global trends, while tide gauges provide high-precision, localized measurements. This combination allows scientists to cross-check and validate findings from satellite altimetry with millimeter-level measurements.
Ocean Thermal Expansion & Ice Melt Tracking Satellite altimeters track sea-level changes largely driven by ocean thermal expansion and melting ice contributions. While individual wave measurements might have ±2–5 cm precision, the changes driven by these processes (ice melt and warming) manifest as consistent, detectable trends over time using satellite observations. Key Insight: Although satellite altimeters have limitations in instantaneous precision (e.g., a 5 cm accuracy range), temporal averaging, statistical methods, and the spatial scale of observations make them capable of reliably detecting millimeter-scale global sea-level rise trends over time. They do this by focusing on global patterns, long-term averages, and statistical analyses rather than relying solely on absolute single-point precision.

You said: Don't you think the reason for switching from tide gages to satellite measurements is because the satellite data appears to support the man-made global warming theory, whereas the long-term tide gage data does not? ChatGPT said: ChatGPT You raise an interesting perspective that touches on the debate surrounding climate science, data interpretation, and historical measurements. However, the shift from tide gauges to satellite altimetry for global sea-level monitoring is primarily driven by the limitations of tide gauges in terms of spatial coverage and comprehensiveness, not political or theoretical motivations.

Reasons for the Shift from Tide Gauges to Satellite Measurements: Limited Geographic Coverage of Tide Gauges:

Tide gauges are distributed unevenly around the world, with denser networks in certain regions (e.g., near urbanized coastlines) and sparse networks in others, such as parts of the Southern Hemisphere and remote areas. This uneven distribution made it difficult to achieve global sea-level trends with tide gauges alone. Satellite Altimetry Provides Comprehensive Global Coverage:

Satellites can observe global sea-level patterns across oceans, even in regions where tide gauges are absent. A satellite can measure the sea surface height across the entire globe consistently, while tide gauges are limited to specific points. Higher Temporal Resolution with Satellites:

Tide gauges can have data gaps or inconsistencies due to equipment maintenance, sea-level anomalies at localized sites, or subsidence. Satellite measurements provide continuous, reliable observations over time, improving the consistency of long-term trends. Improved Technological Capacity:

Satellite altimeters have evolved to provide highly accurate and repeatable observations over time. Though their vertical precision is in the range of centimeters (rather than millimeters in single measurements), the statistical strength of repeated satellite measurements over large spatial scales makes them more powerful for identifying trends over decades. Addressing the Idea of Supporting Theories: It is true that human-induced climate change theories predict rising sea levels due to greenhouse gas emissions, melting ice, and ocean warming. However:

Tide gauge data, when analyzed over long periods, also shows sea-level rise, although at a somewhat slower rate than satellite data suggests due to the limitations of localized measurements. The historical record from tide gauges (dating back more than a century) has consistently indicated sea-level changes, consistent with the understanding that sea-level rise is a response to long-term climate changes.

The differences between satellite observations and tide gauge measurements can be attributed to factors like thermal expansion effects, glacial melting contributions, regional variability, and changes in oceanic processes, rather than any manipulation of data or intentional bias.

Satellite data aligns with established climate models based on physical science principles such as global warming's effect on ice sheets, thermal expansion of seawater, and other factors, not because the data was chosen or manipulated to support a hypothesis.

Science and its Self-Checking Mechanisms: Climate science, like all scientific fields, uses multiple independent lines of evidence to verify conclusions:

Satellite data provides global, high-resolution monitoring. Tide gauge observations offer localized, historical insights. Climate models, ice core data, geological evidence, and paleoclimate studies provide additional support to the understanding of sea-level changes over geological timescales. When all these sources align and point toward rising sea levels due to a mix of natural processes and anthropogenic contributions, it strengthens the scientific consensus—not because the data was forced to match a narrative but because independent evidence supports these findings.

Final Thoughts: The transition to satellite altimetry was driven by scientific needs for spatial coverage, temporal consistency, and technological advances, not political motives. While you bring up a valid point about skepticism in science (a healthy part of scientific inquiry!), the use of satellite altimetry is grounded in improving observational capabilities rather than supporting a specific theory.

Both tide gauge data and satellite observations, when carefully analyzed, tell a consistent story of global sea-level rise, driven by natural processes and human-induced warming. The scientific discussion focuses on understanding the rates, causes, and impacts—not on proving a predetermined theory through data manipulation.

You said: If the global rate of sea-level rise is increasing, as determined by the satellite data, why don't tide gages show the same rate of sea-level rise? ChatGPT said: ChatGPT That's a thoughtful and well-informed question! The discrepancy between satellite measurements of global sea-level rise and tide gauge observations arises primarily from spatial variability, regional effects, and the differing nature of these data networks. Let's break this down:

Differences in Coverage: Global vs. Localized Observations Satellite altimetry measures sea surface height globally across vast regions of oceans, with continuous observations over time.

Tide gauges, however, are localized measurements at specific coastal points. They do not provide a global, uniform view of sea-level changes.

Tide gauges are often clustered in certain regions (near urbanized coastlines or shipping routes) and absent in others. These uneven distributions can lead to regional biases that affect average trends.

Satellite data, by contrast, samples the entire global ocean and thus offers a more uniform global trend.

Regional Sea-Level Variability Sea levels don't rise uniformly everywhere due to factors like ocean circulation patterns, melting ice distribution, and geological effects like isostatic rebound (land sinking or rising in response to changes in ice weight). Examples: Land subsidence can make local sea levels appear to rise faster than global averages. Conversely, regional variations in ocean circulation can lead to areas where sea levels might rise more slowly or even remain stable, even as global average sea levels are rising. Tide gauges capture these regional effects at their specific locations, while satellites average over broader areas, making global patterns more detectable.
Time Lag in Observations Some tide gauges have been operating for over a century, capturing historical sea-level trends that may reflect a mix of natural variability and regional effects.

Satellite altimeters, on the other hand, started their global measurements in the late 20th century (from the 1990s onward), focusing on recent trends.

A mismatch in time periods between tide gauges and satellite observations can sometimes lead to observed differences.

Land Motion (Subsidence and Uplift) Local land subsidence (sinking of the land) or uplift (rise of the land) can influence tide gauge measurement

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– PhDinNY [S] 1 point 13 days ago +1 / -0

A mismatch in time periods between tide gauges and satellite observations can sometimes lead to observed differences.

Land Motion (Subsidence and Uplift) Local land subsidence (sinking of the land) or uplift (rise of the land) can influence tide gauge measurements: In areas experiencing subsidence, sea-level rise appears accelerated because the land is sinking. Conversely, land uplift can make sea-level rise appear slower at local tide gauge locations. This effect is highly localized and doesn't align with the global trends observed by satellite measurements.
Human Engineering and Coastal Changes Local human interventions (e.g., construction, damming, or dredging) can also alter local sea-level trends. Tide gauge data can reflect these localized effects, which are not captured by global satellite data. Summarizing the Discrepancy: The apparent difference between satellite data and tide gauge measurements arises from:

Broader global spatial sampling by satellites compared to the local nature of tide gauges. Regional oceanic and climatic variability that affects localized observations but averages out on a global scale. Geological effects, such as subsidence and isostatic rebound, impacting localized tide gauge measurements. Differences in time periods between the start of satellite altimetry observations and the long-term records of tide gauges. Localized human impacts and engineering efforts. Key Point While tide gauge data may show slower rates of sea-level change in certain regions or fail to capture rapid global trends, this doesn't disprove the satellite-based global observations. Instead, satellite altimeters provide a more comprehensive, unbiased global average, while tide gauges give insight into regional patterns and long-term localized trends.

The combination of these two approaches—tide gauge data for historical context and satellite measurements for global trends—provides a more complete picture of global sea-level rise and its complex regional variations.

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– Nytridr 1 point 12 days ago +1 / -0

Anyone that's ever tried to remove dents from their 2-stroke exhaust pipes knows that filling them with water and throwing them in an ice chest that water expands when frozen,q causing the water to expand and push the dents outwardly. Water then contracts again at higher temps and expands again when boiled.. If the ice caps melt then wouldn't we have lower sea levels? I mean the sea's would have to be boiling for them to expand/rise sea levels

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