**3. Methodology**

The study utilized the qualitative design and uses document analysis approach of the data collected from the existing documented secondary sources. Resources were collected via use of Research for Life search engine, mostly peer-review journals and accredited resources were used in finding the useable data. Data were collected from more than fifteen different sources. Primarily the main sources of the collected data included Journal article titled "Global warming and climate change: Realities, Uncertainties and Measures" by A. P. Alzebeokhai, published in 2009, data from the NASA-Global climate change, data from NOAA (National centers for environmental information: National oceanic and atmospheric administration), and Intergovernmental Panel on Climate Change (IPCC) (latest and updated information as of 2019).

The data collection and analysis are done in line with the research question on "Is Global warming and climate change (GWCC) really occurring, and how urgent it is?" Data from several climate expert organizations such as NASA-Global climate change, IPCC, NOAA and other accredited scientific journals are used for the same. The data from those separate sources were compared and analyzed. Owing to the lack of primary data, no statistical software was employed for the analysis.

## **4. Result and discussion**

The result from the analysis of four separate sets of observations, including surface temperature measurements, sea surface temperature, sea level changes, and temperature profiles in boreholes, all indicate that the earth's surface temperature is increasing, suggesting that it is warming. Each of these separate sets of observations yields findings that overlap and complement each other, suggesting that the GWCC is a real phenomenon.

#### **4.1 Surface temperature**

The surface of the earth has warmed by an average of 1.0°C (1.8°F) in the last 100 years, according to regular measurements of the earth's surface temperature recorded daily from thousands of weather stations around the world, both ashore and stumped. Mean weekly, monthly, and annual temperatures are calculated using daily temperature measurements. As a result, the average annual temperature change can be easily monitored from year to year. The global mean temperature has risen by 0.1°C per decade over the last two decades, with 2005 being the warmest year on record [7]. The effects of large population centers on global mean temperature, referred to as the "urban heat island effect," are calculated and corrected for; however, this accounts for less than 15% of observed global warming. Global warming is not constant across the globe, both in terms of time and space; high latitude regions warm more than low latitude regions [7]. Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels, with a likely range of 0.8°C to 1.2°C. Global temperature rise is likely to reach 1.5°C between 2030 and 2052, if it continues to increase at the current rate [15]. Moreover, according to the Global climate change report 2018 [23], complied by NOAA, shows that the surface temperature is increasing, the data compared the temperature recorded from 1880 till 2018 which showed that, 2016 is the warmest recorded temperature with 0.95 temperature anomaly degree Celsius, followed by 2015 with 0.91 anomaly degree Celsius, and 2017 with 0.85 anomaly degree Celsius [23].

Additionally, the data from three major compilations based on measured surface temperatures: from GISS (Goddard institute for space studies), HadCRU (global temperature dataset) and NCDC (national oceanic and atmospheric administration) showed upward trend (see **Figure 2**). They have expressed the trend as the temperature difference ("anomaly") with respect to the 1901–2000 average as the baseline [24].

The comparison of the three different dataset form three climate recoding source showed that the temperatures juggle up and down, but the overall trend is upward meaning the globe is warming.

Upon analysing trend through the average of the three datasets over the period 1975–2009 (during which greenhouse gas forcing was the dominant driver of climate change), the following are (see **Figure 3**).

For all three-temperature series, the trend from 1975 to 2009 is about the same (0.17 +/− 0.03 degrees per decade)*.* The error reflects the trend's 95 percent confidence interval, i.e., if the trend analysis were repeated a hundred times on the actual underlying results, the trend will be within the range of 0.14 to 0.20 degrees per decade 95 times out of 100 (see **Figure 3**) [24].

*Global Warming and Climate Change (GWCC) Realities DOI: http://dx.doi.org/10.5772/intechopen.97820*

#### **Figure 2.**

*Comparison of three data set on surface temperature (source: Verheggen [24]).*

#### **Figure 3.**

*Showing average temperature from three dataset (source: Verheggen [24]).*

The thin black lines (see **Figure 3**) represent the 95% confidence "predictions bands" for the data. Based on the observed variability, 95% of the data are expected to fall within these lines. The observed yearly variability in global temperatures (occasionally exceeding 0.2 degrees) is such that 10 years is too short to discern the underlying long-term trend (0.17 degrees per decade) [24]. Thus, data from all different sources shows and depicts that the surface temperature of the earth has increased over the decade, with different data source agreeing to the value range of 0.1°C increase per decade [24]. This indicates the occurrence of global warming.

#### **4.2 Sea level rise**

Another predictor of global warming and climate change comes from a completely different series of findings (the measurements of water level changes). The amount of water in the oceans is rising as a result of thermal expansion of water within the oceans and, as well as due to, melting of glaciers and polar ice as the earth warms.

#### **Figure 4.**

*Mean annual sea level rise associated with the thermal expansion of sea water due to warming and widespread melting of ice sheets (source: Aizebeokhai [7]).*

#### **Figure 5.**

*Trend of increase in sea level (satellite data) (source: NASA-global climate change [25]).*

Regular water level observations are taken at various sites, equivalent to temperature measurements; daily water level variations, mostly due to tides and storms, are averaged to obtain mean sea level for a given period of time. **Figure 4** depicts the average annual change in sea level between 1880 and 2008. Over the last century, the average water level has risen by around 18 cm [7]. Between 1880 and 1990, it increased by an estimated 2 mm per year on average (left chart in **Figure 4**) and is now growing at a rate of about 3.4 mm per year (right chart in **Figure 4**). Similar to global temperature changes, sea level changes, aren't constant, so the detailed changes aren't always in line with surface temperature measurements. The thermal expansion of the water column occurs later than the associated change in surface temperature, with ocean currents influencing the timing. Global temperature changes, as well as changes in sea level, are not constant, and the details of these changes are not always in line with surface temperature measurements. The water column's thermal expansion occurs later than the related change in surface temperature; the differences are affected by ocean currents (**Figure 5**) [7].

Furthermore, the latest data from the NASA-Global Climate Change, shows that the trend of sea level is upward and increasing. The increase rate of 3.3 mm per year is recorded [25]. Thus, the data from the existing sources both form past and the recent, indicates the rise in the sea level, agreeing to rise value range of 2 to 3.4 mm per year. Which hints to the occurrence of the global warming and retreat of the ice sheets and glaciers.
