Explanation:

Statement 1: The transport sector is the largest contributor to GHG emissions.

- The statement is true. The transport sector is indeed the largest contributor to greenhouse gas (GHG) emissions.
- The transport sector includes various modes of transportation such as cars, trucks, ships, airplanes, and trains. These modes of transportation primarily rely on fossil fuels, such as gasoline and diesel, which release carbon dioxide (CO2) and other GHGs when burned.
- According to the Intergovernmental Panel on Climate Change (IPCC), the transport sector accounted for approximately 24% of global energy-related CO2 emissions in 2016, making it the largest contributor among all sectors.
- The rapid growth in the number of vehicles, especially in developing countries, has led to a significant increase in GHG emissions from the transport sector. As a result, reducing emissions from this sector has become a key focus in mitigating climate change.

Statement 2: CO2 concentration is higher than any other GHG.

- The statement is false. While carbon dioxide (CO2) is one of the most abundant greenhouse gases, it is not necessarily higher in concentration than other GHGs.
- Other important GHGs include methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). These gases have different global warming potentials (GWP) and lifetimes in the atmosphere.
- Methane, for example, has a much higher GWP than CO2 over a 20-year time period, although its concentration in the atmosphere is much lower. Methane is primarily emitted from sources such as livestock, rice cultivation, and the extraction and transport of fossil fuels.
- Nitrous oxide, another potent GHG, is released from agricultural and industrial activities, as well as the burning of fossil fuels and solid waste.
- The concentrations of these GHGs and their impacts on climate change are assessed by scientific organizations such as the IPCC. The global concentrations of GHGs are measured in parts per million (ppm) or parts per billion (ppb).

In conclusion, statement 1 is true as the transport sector is indeed the largest contributor to GHG emissions. However, statement 2 is false as CO2 concentration is not necessarily higher than other GHGs.